diff --git a/src/backup.go b/src/backup.go
index 10c6102..57c03f2 100644
--- a/src/backup.go
+++ b/src/backup.go
@@ -148,8 +148,8 @@ func xteveRestore(archive string) (newWebURL string, err error) {
 		return
 	}
 
-	backupVersion = newConfig["version"].(string)
-	if backupVersion < System.Compatibility {
+	backupVersion, ok := newConfig["version"].(string)
+	if !ok || backupVersion < System.Compatibility {
 		err = errors.New(getErrMsg(1013))
 		return
 	}
@@ -167,7 +167,11 @@ func xteveRestore(archive string) (newWebURL string, err error) {
 		return
 	}
 
-	newPort = newConfig["port"].(string)
+	newPort, ok = newConfig["port"].(string)
+	if !ok {
+		err = errors.New(getErrMsg(1030))
+		return
+	}
 	oldPort = Settings.Port
 
 	if newPort == oldPort {
diff --git a/src/data.go b/src/data.go
index 37e4c61..31d69cb 100644
--- a/src/data.go
+++ b/src/data.go
@@ -63,17 +63,31 @@ func updateServerSettings(request RequestStruct) (settings SettingsStruct, err e
 				// Leerzeichen aus den Werten entfernen und Formatierung der Uhrzeit überprüfen (0000 - 2359)
 				var newUpdateTimes = make([]string, 0)
 
-				for _, v := range value.([]any) {
+				updateTimes, ok := value.([]any)
+				if !ok {
+					err = errors.New(getErrMsg(1012))
+					ShowError(err, 1012)
+					return Settings, err
+				}
 
-					v = strings.Replace(v.(string), " ", "", -1)
+				for _, v := range updateTimes {
 
-					_, err := time.Parse("1504", v.(string))
+					t, ok := v.(string)
+					if !ok {
+						err = errors.New(getErrMsg(1012))
+						ShowError(err, 1012)
+						return Settings, err
+					}
+
+					t = strings.Replace(t, " ", "", -1)
+
+					_, err := time.Parse("1504", t)
 					if err != nil {
 						ShowError(err, 1012)
 						return Settings, err
 					}
 
-					newUpdateTimes = append(newUpdateTimes, v.(string))
+					newUpdateTimes = append(newUpdateTimes, t)
 
 				}
 
@@ -320,21 +334,30 @@ func saveFiles(request RequestStruct, fileType string) (err error) {
 
 	for dataID, data := range newData {
 
+		dataMap, ok := data.(map[string]any)
+		if !ok {
+			err = errors.New(getErrMsg(1020))
+			return
+		}
+
 		if dataID == "-" {
 
 			// Neue Providerdatei
 			dataID = indicator + randomString(19)
-			data.(map[string]any)["new"] = true
-			filesMap[dataID] = data
+			dataMap["new"] = true
+			filesMap[dataID] = dataMap
 
 		} else {
 
 			// Bereits vorhandene Providerdatei
-			for key, value := range data.(map[string]any) {
+			oldData, ok := filesMap[dataID].(map[string]any)
+			if !ok {
+				// Unknown file ID: nothing to update.
+				continue
+			}
 
-				var oldData = filesMap[dataID].(map[string]any)
+			for key, value := range dataMap {
 				oldData[key] = value
-
 			}
 
 		}
@@ -353,11 +376,11 @@ func saveFiles(request RequestStruct, fileType string) (err error) {
 		}
 
 		// Neue Providerdatei
-		if _, ok := data.(map[string]any)["new"]; ok {
+		if _, ok := dataMap["new"]; ok {
 
 			reloadData = true
 			err = getProviderData(fileType, dataID)
-			delete(data.(map[string]any), "new")
+			delete(dataMap, "new")
 
 			if err != nil {
 				delete(filesMap, dataID)
@@ -661,8 +684,16 @@ func saveUserData(request RequestStruct) (err error) {
 func saveNewUser(request RequestStruct) (err error) {
 
 	var data = request.UserData
-	var username = data["username"].(string)
-	var password = data["password"].(string)
+
+	username, ok := data["username"].(string)
+	if !ok {
+		return errors.New("Username is missing")
+	}
+
+	password, ok := data["password"].(string)
+	if !ok {
+		return errors.New("Password is missing")
+	}
 
 	delete(data, "password")
 	delete(data, "confirm")
@@ -855,7 +886,7 @@ func buildDatabaseDVR() (err error) {
 
 		var playlistFile = getLocalProviderFiles(fileType)
 
-		for n, i := range playlistFile {
+		for _, i := range playlistFile {
 
 			var channels []any
 			var groupTitle, tvgID, uuid = 0, 0, 0
@@ -878,7 +909,8 @@ func buildDatabaseDVR() (err error) {
 				ShowError(err, 1005)
 				err = errors.New(playlistName + ": Local copy of the file no longer exists")
 				ShowError(err, 0)
-				playlistFile = append(playlistFile[:n], playlistFile[n+1:]...)
+				// playlistFile is not used after this loop; removing the entry
+				// while ranging over it only skipped the following file.
 			}
 
 			// Streams analysieren
diff --git a/src/httpclient.go b/src/httpclient.go
new file mode 100644
index 0000000..3652db1
--- /dev/null
+++ b/src/httpclient.go
@@ -0,0 +1,14 @@
+package src
+
+import (
+	"net/http"
+	"time"
+)
+
+// providerHTTPClient : Downloads of provider files (M3U, XMLTV, HDHR lineup).
+// Playlists and EPG files can be large, so the overall timeout is generous;
+// it only exists so a stalled provider cannot hang an update forever.
+var providerHTTPClient = &http.Client{Timeout: 5 * time.Minute}
+
+// apiHTTPClient : Short request/response calls to other services (Plex API).
+var apiHTTPClient = &http.Client{Timeout: 30 * time.Second}
diff --git a/src/internal/authentication/atomic_test.go b/src/internal/authentication/atomic_test.go
new file mode 100644
index 0000000..4cb3295
--- /dev/null
+++ b/src/internal/authentication/atomic_test.go
@@ -0,0 +1,43 @@
+package authentication
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWriteFileAtomic(t *testing.T) {
+	dir := t.TempDir()
+	file := filepath.Join(dir, "authentication.json")
+
+	if err := writeFileAtomic(file, []byte("{\"a\":1}"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	if err := writeFileAtomic(file, []byte("{\"a\":2}"), 0600); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := os.ReadFile(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "{\"a\":2}" {
+		t.Errorf("content = %q", got)
+	}
+
+	fi, err := os.Stat(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fi.Mode().Perm() != 0600 {
+		t.Errorf("mode = %o, want 0600", fi.Mode().Perm())
+	}
+
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 1 {
+		t.Errorf("expected only the target file, found %d entries", len(entries))
+	}
+}
diff --git a/src/internal/authentication/authentication.go b/src/internal/authentication/authentication.go
index b55cf3c..f51590a 100755
--- a/src/internal/authentication/authentication.go
+++ b/src/internal/authentication/authentication.go
@@ -411,11 +411,47 @@ func saveDatabase(tmpMap any) (err error) {
 		return
 	}
 
-	err = os.WriteFile(database, []byte(jsonString), 0600)
+	err = writeFileAtomic(database, []byte(jsonString), 0600)
+
+	return
+}
+
+// writeFileAtomic : Temp file + fsync + rename, so authentication.json is
+// never observed half-written. (Private copy; this package cannot import src.)
+func writeFileAtomic(name string, data []byte, perm os.FileMode) (err error) {
+
+	tmp, err := os.CreateTemp(filepath.Dir(name), ".tmp-*")
 	if err != nil {
 		return
 	}
 
+	var tmpName = tmp.Name()
+
+	defer func() {
+		if err != nil {
+			tmp.Close()
+			os.Remove(tmpName)
+		}
+	}()
+
+	if _, err = tmp.Write(data); err != nil {
+		return
+	}
+
+	if err = tmp.Sync(); err != nil {
+		return
+	}
+
+	if err = tmp.Close(); err != nil {
+		return
+	}
+
+	if err = os.Chmod(tmpName, perm); err != nil {
+		return
+	}
+
+	err = os.Rename(tmpName, name)
+
 	return
 }
 
diff --git a/src/internal/imgcache/cache.go b/src/internal/imgcache/cache.go
index 94a5451..80d2ef6 100644
--- a/src/internal/imgcache/cache.go
+++ b/src/internal/imgcache/cache.go
@@ -9,8 +9,14 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 )
 
+// httpClient : Client for logo downloads. Providers occasionally serve
+// images from hosts that never answer; without a timeout the caching
+// goroutine would hang forever.
+var httpClient = &http.Client{Timeout: 30 * time.Second}
+
 // Cache : Cache strcut
 type Cache struct {
 	path     string
@@ -41,8 +47,6 @@ func New(path, chacheURL string, caching bool) (c *Cache, err error) {
 	c.Queue = []string{}
 	c.Cache = []string{}
 
-	var queue []string
-
 	c.Image.GetURL = func(src string) (cacheURL string) {
 
 		c.Lock()
@@ -89,50 +93,30 @@ func New(path, chacheURL string, caching bool) (c *Cache, err error) {
 		return src
 	}
 
+	// Caching downloads every queued image. The lock is only held while the
+	// queue is copied and while the map / queue are updated per image; the
+	// HTTP download and file write happen unlocked so GetURL callers (M3U /
+	// XMLTV generation) are not blocked for the duration of the downloads.
 	c.Image.Caching = func() {
 
 		c.Lock()
-		defer c.Unlock()
+		var queue = make([]string, len(c.Queue))
+		copy(queue, c.Queue)
+		c.Unlock()
 
-		var filename string
+		for _, src := range queue {
 
-		for _, src := range c.Queue {
-
-			resp, err := http.Get(src)
+			filename, err := c.download(src)
 			if err != nil {
-				continue
-			}
-			defer resp.Body.Close()
-
-			if resp.StatusCode != http.StatusOK {
+				// Stays in the queue and is retried on the next run.
 				continue
 			}
 
-			filename = fmt.Sprintf("%s%s%s%s", c.path, string(os.PathSeparator), strToMD5(src), filepath.Ext(src))
+			c.Lock()
+			c.images[filename] = c.cacheURL + filename
+			c.Queue = removeStringFromSlice(src, c.Queue)
+			c.Unlock()
 
-			file, err := os.Create(filename)
-			if err != nil {
-				continue
-			}
-
-			defer file.Close()
-
-			_, err = io.Copy(file, resp.Body)
-			if err != nil {
-				continue
-			}
-
-			u, err := url.Parse(src)
-			if err == nil {
-				c.images[fmt.Sprintf("%s%s", strToMD5(src), filepath.Ext(u.Path))] = c.cacheURL + filename
-			}
-
-			queue = append(queue, src)
-
-		}
-
-		for _, q := range queue {
-			c.Queue = removeStringFromSlice(q, c.Queue)
 		}
 
 	}
@@ -175,3 +159,45 @@ func New(path, chacheURL string, caching bool) (c *Cache, err error) {
 
 	return
 }
+
+// download : Fetches src into the cache folder and returns the cached file
+// name (md5 of the URL plus the extension of the URL path). Must be called
+// without holding the lock.
+func (c *Cache) download(src string) (filename string, err error) {
+
+	u, err := url.Parse(src)
+	if err != nil {
+		return
+	}
+
+	filename = fmt.Sprintf("%s%s", strToMD5(src), filepath.Ext(u.Path))
+
+	resp, err := httpClient.Get(src)
+	if err != nil {
+		return
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		err = fmt.Errorf("%s: %s", src, resp.Status)
+		return
+	}
+
+	var path = filepath.Join(c.path, filename)
+
+	file, err := os.Create(path)
+	if err != nil {
+		return
+	}
+
+	_, err = io.Copy(file, resp.Body)
+	if closeErr := file.Close(); err == nil {
+		err = closeErr
+	}
+
+	if err != nil {
+		os.Remove(path)
+	}
+
+	return
+}
diff --git a/src/plex_api.go b/src/plex_api.go
index e1169f7..2784ec8 100644
--- a/src/plex_api.go
+++ b/src/plex_api.go
@@ -342,11 +342,7 @@ func doPlexRequest(method, baseURL, endpoint, token string) (status int, body []
 		req.Header.Set("X-Plex-Version", System.Version)
 	}
 
-	client := &http.Client{
-		Timeout: 10 * time.Second,
-	}
-
-	resp, err := client.Do(req)
+	resp, err := apiHTTPClient.Do(req)
 	if err != nil {
 		return
 	}
diff --git a/src/provider.go b/src/provider.go
index d7cf508..b5f3cad 100644
--- a/src/provider.go
+++ b/src/provider.go
@@ -142,8 +142,16 @@ func getProviderData(fileType, fileID string) (err error) {
 
 	for dataID, d := range dataMap {
 
-		var data = d.(map[string]any)
-		var fileSource = data["file.source"].(string)
+		data, ok := d.(map[string]any)
+		if !ok {
+			continue
+		}
+
+		fileSource, ok := data["file.source"].(string)
+		if !ok {
+			continue
+		}
+
 		newProvider = false
 
 		if _, ok := data["new"]; ok {
@@ -224,8 +232,8 @@ func getProviderData(fileType, fileID string) (err error) {
 				if value, ok := dataMap[dataID].(map[string]any); ok {
 
 					data = value
-					data["counter.error"] = data["counter.error"].(float64) + 1
-					data["counter.download"] = data["counter.download"].(float64) + 1
+					data["counter.error"] = toFloat64(data["counter.error"]) + 1
+					data["counter.download"] = toFloat64(data["counter.download"]) + 1
 
 				}
 
@@ -243,10 +251,13 @@ func getProviderData(fileType, fileID string) (err error) {
 				var data = make(map[string]any)
 				data = value
 
-				if data["counter.error"].(float64) == 0 {
+				var errCount = toFloat64(data["counter.error"])
+				var dlCount = toFloat64(data["counter.download"])
+
+				if errCount == 0 || dlCount == 0 {
 					data["provider.availability"] = 100
 				} else {
-					data["provider.availability"] = int(data["counter.error"].(float64)*100/data["counter.download"].(float64)*-1 + 100)
+					data["provider.availability"] = int(errCount*100/dlCount*-1 + 100)
 				}
 
 			}
@@ -289,8 +300,7 @@ func downloadFileFromServer(providerURL string) (filename string, body []byte, e
 
 	req.Header.Set("User-Agent", getUserAgent())
 
-	client := &http.Client{}
-	resp, err := client.Do(req)
+	resp, err := providerHTTPClient.Do(req)
 	if err != nil {
 		return
 	}
@@ -307,15 +317,22 @@ func downloadFileFromServer(providerURL string) (filename string, body []byte, e
 
 	if index > -1 {
 
-		var headerFilename = resp.Header.Get("Content-Disposition")[index:len(resp.Header.Get("Content-Disposition"))]
-		var value = strings.Split(headerFilename, `=`)
-		var f = strings.Replace(value[1], `"`, "", -1)
+		var headerFilename = resp.Header.Get("Content-Disposition")[index:]
+		var value = strings.SplitN(headerFilename, `=`, 2)
 
-		f = strings.Replace(f, `;`, "", -1)
-		filename = f
-		showInfo("Header filename:" + filename)
+		if len(value) == 2 {
 
-	} else {
+			var f = strings.Replace(value[1], `"`, "", -1)
+
+			f = strings.Replace(f, `;`, "", -1)
+			filename = f
+			showInfo("Header filename:" + filename)
+
+		}
+
+	}
+
+	if len(filename) == 0 {
 
 		var cleanFilename = strings.SplitN(getFilenameFromPath(providerURL), "?", 2)
 		filename = cleanFilename[0]
diff --git a/src/screen.go b/src/screen.go
index 55c6ec7..cc04ddc 100644
--- a/src/screen.go
+++ b/src/screen.go
@@ -10,6 +10,82 @@ import (
 	"time"
 )
 
+// logMu guards WebScreenLog (its slice and counters) and System.Notification.
+// Log lines are appended from every goroutine (buffer, maintenance, web
+// handlers) and read by the websocket handler.
+var logMu sync.Mutex
+
+// logAppend : Appends a timestamped line to the in-memory log and trims it
+// to Settings.LogEntriesRAM.
+func logAppend(logMsg string) {
+
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	WebScreenLog.Log = append(WebScreenLog.Log, time.Now().Format("2006-01-02 15:04:05")+" "+logMsg)
+	logCleanUpLocked()
+}
+
+// logAppendCounted : Appends a warning / error line and bumps the matching
+// counter. Like the original code this does not trim the log; the next
+// info / debug line does.
+func logAppendCounted(logMsg string, isError bool) {
+
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	WebScreenLog.Log = append(WebScreenLog.Log, time.Now().Format("2006-01-02 15:04:05")+" "+logMsg)
+
+	if isError {
+		WebScreenLog.Errors++
+	} else {
+		WebScreenLog.Warnings++
+	}
+}
+
+// resetWebScreenLog : Clears the in-memory log and its counters.
+func resetWebScreenLog() {
+
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	WebScreenLog.Log = make([]string, 0)
+	WebScreenLog.Errors = 0
+	WebScreenLog.Warnings = 0
+}
+
+// webScreenLogSnapshot : Copy of the log for the web client. The slice is
+// copied so the JSON encoder never races with a concurrent append.
+func webScreenLogSnapshot() (snapshot WebScreenLogStruct) {
+
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	snapshot = WebScreenLog
+	snapshot.Log = make([]string, len(WebScreenLog.Log))
+	copy(snapshot.Log, WebScreenLog.Log)
+
+	return
+}
+
+// notificationsSnapshot : Copy of the notifications map for the web client.
+func notificationsSnapshot() (snapshot map[string]Notification) {
+
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	if System.Notification == nil {
+		return nil
+	}
+
+	snapshot = make(map[string]Notification, len(System.Notification))
+	for k, v := range System.Notification {
+		snapshot[k] = v
+	}
+
+	return
+}
+
 func showInfo(str string) {
 
 	if System.Flag.Info {
@@ -33,9 +109,7 @@ func showInfo(str string) {
 
 		printLogOnScreen(logMsg, "info")
 
-		logMsg = strings.Replace(logMsg, " ", "&nbsp;", -1)
-		WebScreenLog.Log = append(WebScreenLog.Log, time.Now().Format("2006-01-02 15:04:05")+" "+logMsg)
-		logCleanUp()
+		logAppend(strings.Replace(logMsg, " ", "&nbsp;", -1))
 
 	}
 
@@ -51,7 +125,6 @@ func showDebug(str string, level int) {
 	var msg = strings.SplitN(str, ":", 2)
 	var length = len(msg[0])
 	var space string
-	var mutex = sync.RWMutex{}
 
 	if len(msg) == 2 {
 
@@ -64,11 +137,7 @@ func showDebug(str string, level int) {
 
 		printLogOnScreen(logMsg, "debug")
 
-		mutex.Lock()
-		logMsg = strings.Replace(logMsg, " ", "&nbsp;", -1)
-		WebScreenLog.Log = append(WebScreenLog.Log, time.Now().Format("2006-01-02 15:04:05")+" "+logMsg)
-		logCleanUp()
-		mutex.Unlock()
+		logAppend(strings.Replace(logMsg, " ", "&nbsp;", -1))
 
 	}
 
@@ -99,7 +168,8 @@ func showHighlight(str string) {
 	}
 
 	notification.Type = "info"
-	notification.Message = msg[1]
+	// Messages without a "key:value" prefix are shown as they are.
+	notification.Message = msg[len(msg)-1]
 
 	addNotification(notification)
 
@@ -109,31 +179,22 @@ func showWarning(errCode int) {
 
 	var errMsg = getErrMsg(errCode)
 	var logMsg = fmt.Sprintf("[%s] [WARNING] %s", System.Name, errMsg)
-	var mutex = sync.RWMutex{}
 
 	printLogOnScreen(logMsg, "warning")
 
-	mutex.Lock()
-	WebScreenLog.Log = append(WebScreenLog.Log, time.Now().Format("2006-01-02 15:04:05")+" "+logMsg)
-	WebScreenLog.Warnings++
-	mutex.Unlock()
+	logAppendCounted(logMsg, false)
 
 }
 
 // ShowError : Zeigt die Fehlermeldungen in der Konsole
 func ShowError(err error, errCode int) {
 
-	var mutex = sync.RWMutex{}
-
 	var errMsg = getErrMsg(errCode)
 	var logMsg = fmt.Sprintf("[%s] [ERROR] %s (%s) - EC: %d", System.Name, err, errMsg, errCode)
 
 	printLogOnScreen(logMsg, "error")
 
-	mutex.Lock()
-	WebScreenLog.Log = append(WebScreenLog.Log, time.Now().Format("2006-01-02 15:04:05")+" "+logMsg)
-	WebScreenLog.Errors++
-	mutex.Unlock()
+	logAppendCounted(logMsg, true)
 
 }
 
@@ -174,24 +235,17 @@ func printLogOnScreen(logMsg string, logType string) {
 
 }
 
-func logCleanUp() {
+// logCleanUpLocked : Trims the log to the newest Settings.LogEntriesRAM
+// lines and recounts warnings / errors. The caller must hold logMu.
+func logCleanUpLocked() {
+
+	WebScreenLog.Log = keepLastEntries(WebScreenLog.Log, Settings.LogEntriesRAM)
 
-	var logEntriesRAM = Settings.LogEntriesRAM
 	var logs = WebScreenLog.Log
 
 	WebScreenLog.Warnings = 0
 	WebScreenLog.Errors = 0
 
-	if len(logs) > logEntriesRAM {
-
-		var tmp = make([]string, 0)
-		for i := len(logs) - logEntriesRAM; i < logEntriesRAM; i++ {
-			tmp = append(tmp, logs[i])
-		}
-
-		logs = tmp
-	}
-
 	for _, log := range logs {
 
 		if strings.Contains(log, "WARNING") {
@@ -204,8 +258,25 @@ func logCleanUp() {
 
 	}
 
-	WebScreenLog.Log = logs
+}
 
+// keepLastEntries : Returns the last max entries of logs (a copy, so the
+// old backing array does not keep growing). A max <= 0 keeps nothing, which
+// matches the original behaviour for an unset LogEntriesRAM.
+func keepLastEntries(logs []string, max int) []string {
+
+	if max < 0 {
+		max = 0
+	}
+
+	if len(logs) <= max {
+		return logs
+	}
+
+	var tmp = make([]string, max)
+	copy(tmp, logs[len(logs)-max:])
+
+	return tmp
 }
 
 // Fehlercodes
@@ -386,30 +457,64 @@ func getErrMsg(errCode int) (errMsg string) {
 	return errMsg
 }
 
+// maxNotifications : Number of notifications kept for the web interface.
+const maxNotifications = 10
+
 func addNotification(notification Notification) (err error) {
 
-	var i int
 	var t = time.Now().UnixNano() / (int64(time.Millisecond) / int64(time.Nanosecond))
 	notification.Time = strconv.FormatInt(t, 10)
+
+	insertNotification(notification)
+
+	return
+}
+
+// insertNotification : Stores the notification under its Time key and evicts
+// the oldest ones once more than maxNotifications are kept.
+func insertNotification(notification Notification) {
+
 	notification.New = true
 
 	if len(notification.Headline) == 0 {
 		notification.Headline = strings.ToUpper(notification.Type)
 	}
 
+	logMu.Lock()
+	defer logMu.Unlock()
+
 	if len(System.Notification) == 0 {
 		System.Notification = make(map[string]Notification)
 	}
 
 	System.Notification[notification.Time] = notification
 
-	for key := range System.Notification {
+	for len(System.Notification) > maxNotifications {
+		delete(System.Notification, oldestNotificationKey(System.Notification))
+	}
 
-		if i < len(System.Notification)-10 {
-			delete(System.Notification, key)
+}
+
+// oldestNotificationKey : Key of the notification with the smallest
+// timestamp. Keys are millisecond timestamps as decimal strings; anything
+// that does not parse sorts before everything that does.
+func oldestNotificationKey(notifications map[string]Notification) (oldest string) {
+
+	var oldestTime int64
+	var found bool
+
+	for key, n := range notifications {
+
+		t, err := strconv.ParseInt(n.Time, 10, 64)
+		if err != nil {
+			return key
 		}
 
-		i++
+		if !found || t < oldestTime {
+			oldest = key
+			oldestTime = t
+			found = true
+		}
 
 	}
 
diff --git a/src/screen_test.go b/src/screen_test.go
new file mode 100644
index 0000000..1b85c3c
--- /dev/null
+++ b/src/screen_test.go
@@ -0,0 +1,108 @@
+package src
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func TestKeepLastEntries(t *testing.T) {
+	logs := []string{"1", "2", "3", "4", "5"}
+
+	got := keepLastEntries(logs, 3)
+	if want := []string{"3", "4", "5"}; !reflect.DeepEqual(got, want) {
+		t.Errorf("keepLastEntries(5 entries, 3) = %v, want %v", got, want)
+	}
+
+	if got := keepLastEntries(logs, 10); !reflect.DeepEqual(got, logs) {
+		t.Errorf("keepLastEntries below the limit = %v, want %v", got, logs)
+	}
+
+	if got := keepLastEntries(logs, 0); len(got) != 0 {
+		t.Errorf("keepLastEntries(.., 0) = %v, want empty", got)
+	}
+}
+
+// The ring buffer must keep the newest lines once the log is full; the old
+// loop bound dropped them.
+func TestLogCleanUpKeepsNewest(t *testing.T) {
+	oldLimit := Settings.LogEntriesRAM
+	resetWebScreenLog()
+	t.Cleanup(func() {
+		Settings.LogEntriesRAM = oldLimit
+		resetWebScreenLog()
+	})
+
+	Settings.LogEntriesRAM = 3
+
+	for i := 1; i <= 5; i++ {
+		logAppend(fmt.Sprintf("line-%d", i))
+	}
+
+	snapshot := webScreenLogSnapshot()
+	if len(snapshot.Log) != 3 {
+		t.Fatalf("log has %d entries, want 3: %v", len(snapshot.Log), snapshot.Log)
+	}
+	for i, want := range []string{"line-3", "line-4", "line-5"} {
+		if !strings.HasSuffix(snapshot.Log[i], want) {
+			t.Errorf("entry %d = %q, want suffix %q", i, snapshot.Log[i], want)
+		}
+	}
+
+	// Counters are recomputed from the retained lines.
+	logAppendCounted("[ERROR] boom", true)
+	logAppend("[WARNING] careful")
+	snapshot = webScreenLogSnapshot()
+	if snapshot.Errors != 1 || snapshot.Warnings != 1 {
+		t.Errorf("errors/warnings = %d/%d, want 1/1 (%v)", snapshot.Errors, snapshot.Warnings, snapshot.Log)
+	}
+}
+
+func TestInsertNotificationEvictsOldest(t *testing.T) {
+	old := System.Notification
+	System.Notification = nil
+	t.Cleanup(func() { System.Notification = old })
+
+	// Insert out of order so eviction cannot rely on insertion order.
+	order := []int64{5, 1, 12, 3, 9, 2, 11, 7, 4, 10, 8, 6}
+	for _, ts := range order {
+		insertNotification(Notification{Type: "info", Message: "n", Time: strconv.FormatInt(1000+ts, 10)})
+	}
+
+	got := notificationsSnapshot()
+	if len(got) != maxNotifications {
+		t.Fatalf("kept %d notifications, want %d", len(got), maxNotifications)
+	}
+	for _, ts := range []int64{1, 2} {
+		if _, ok := got[strconv.FormatInt(1000+ts, 10)]; ok {
+			t.Errorf("oldest notification %d should have been evicted", ts)
+		}
+	}
+	for ts := int64(3); ts <= 12; ts++ {
+		if _, ok := got[strconv.FormatInt(1000+ts, 10)]; !ok {
+			t.Errorf("notification %d missing", ts)
+		}
+	}
+
+	// The web-client copy must be independent of the live map.
+	delete(got, "1012")
+	if _, ok := notificationsSnapshot()["1012"]; !ok {
+		t.Error("snapshot is not a copy")
+	}
+}
+
+func TestShowHighlightWithoutColon(t *testing.T) {
+	old := System.Notification
+	System.Notification = nil
+	t.Cleanup(func() { System.Notification = old })
+
+	showHighlight("no separator here") // used to index msg[1] and panic
+
+	for _, n := range notificationsSnapshot() {
+		if n.Message != "no separator here" {
+			t.Errorf("message = %q", n.Message)
+		}
+	}
+}
diff --git a/src/security.go b/src/security.go
index 4c31b46..927b97e 100644
--- a/src/security.go
+++ b/src/security.go
@@ -124,12 +124,7 @@ func maskSettings(s SettingsStruct) SettingsStruct {
 // writePrivateFile : like writeByteToFile but readable only by the owner.
 func writePrivateFile(file string, data []byte) error {
 
-	var filename = getPlatformFile(file)
-
-	if err := os.WriteFile(filename, data, 0600); err != nil {
-		return err
-	}
-
-	// WriteFile keeps the mode of an existing file; tighten it.
-	return os.Chmod(filename, 0600)
+	// The temp file is chmod'ed before the rename, so an existing
+	// world-readable file is replaced by a 0600 one.
+	return writeFileAtomic(getPlatformFile(file), data, 0600)
 }
diff --git a/src/ssdp.go b/src/ssdp.go
index 85e38f2..4dd95a3 100644
--- a/src/ssdp.go
+++ b/src/ssdp.go
@@ -4,12 +4,38 @@ import (
 	"fmt"
 	"log"
 	"os"
-	"os/signal"
+	"sync"
 	"time"
 
 	"github.com/koron/go-ssdp"
 )
 
+// ssdpState : The running advertiser, so Shutdown can say goodbye to the
+// network before the process exits.
+var ssdpState struct {
+	sync.Mutex
+	adv  *ssdp.Advertiser
+	done chan struct{}
+}
+
+// Shutdown : Stops background services (currently the SSDP advertiser).
+// Called from main on SIGINT / SIGTERM.
+func Shutdown() {
+
+	ssdpState.Lock()
+	defer ssdpState.Unlock()
+
+	if ssdpState.adv == nil {
+		return
+	}
+
+	close(ssdpState.done)
+	ssdpState.adv.Bye()
+	ssdpState.adv.Close()
+	ssdpState.adv = nil
+
+}
+
 // SSDP : SSPD / DLNA Server
 func SSDP() (err error) {
 
@@ -19,9 +45,6 @@ func SSDP() (err error) {
 
 	showInfo(fmt.Sprintf("SSDP / DLNA:%t", Settings.SSDP))
 
-	quit := make(chan os.Signal, 1)
-	signal.Notify(quit, os.Interrupt)
-
 	ad, err := ssdp.Advertise(
 		"upnp:rootdevice", // send as "ST"
 		fmt.Sprintf("uuid:%s::upnp:rootdevice", System.DeviceID), // send as "USN"
@@ -38,35 +61,43 @@ func SSDP() (err error) {
 		ssdp.Logger = log.New(os.Stderr, "[SSDP] ", log.LstdFlags)
 	}
 
-	go func(adv *ssdp.Advertiser) {
+	var done = make(chan struct{})
 
-		aliveTick := time.Tick(300 * time.Second)
+	ssdpState.Lock()
+	ssdpState.adv = ad
+	ssdpState.done = done
+	ssdpState.Unlock()
+
+	go func(adv *ssdp.Advertiser, done chan struct{}) {
+
+		aliveTick := time.NewTicker(300 * time.Second)
+		defer aliveTick.Stop()
 
-	loop:
 		for {
 
 			select {
 
-			case <-aliveTick:
-				err = adv.Alive()
-				if err != nil {
-					ShowError(err, 0)
+			case <-aliveTick.C:
+				if aliveErr := adv.Alive(); aliveErr != nil {
+					ShowError(aliveErr, 0)
+					ssdpState.Lock()
+					if ssdpState.adv == adv {
+						ssdpState.adv = nil
+					}
+					ssdpState.Unlock()
 					adv.Bye()
 					adv.Close()
-					break loop
+					return
 				}
 
-			case <-quit:
-				adv.Bye()
-				adv.Close()
-				os.Exit(0)
-				break loop
+			case <-done:
+				return
 
 			}
 
 		}
 
-	}(ad)
+	}(ad, done)
 
 	return
 }
diff --git a/src/toolchain.go b/src/toolchain.go
index baffa25..14db0e3 100644
--- a/src/toolchain.go
+++ b/src/toolchain.go
@@ -204,12 +204,7 @@ func saveMapToJSONFile(file string, tmpMap any) error {
 		return err
 	}
 
-	err = os.WriteFile(filename, []byte(jsonString), 0644)
-	if err != nil {
-		return err
-	}
-
-	return nil
+	return writeFileAtomic(filename, []byte(jsonString), 0644)
 }
 
 func loadJSONFileToMap(file string) (tmpMap map[string]any, err error) {
@@ -229,6 +224,37 @@ func loadJSONFileToMap(file string) (tmpMap map[string]any, err error) {
 	return
 }
 
+// toFloat64 : Numeric value of a JSON decoded field; 0 for anything that
+// is not a number (missing key, wrong type).
+func toFloat64(v any) float64 {
+
+	switch n := v.(type) {
+	case float64:
+		return n
+	case int:
+		return float64(n)
+	case int64:
+		return float64(n)
+	}
+
+	return 0
+}
+
+// removeStrings : Copy of list without the entries present in remove.
+// Order of the remaining entries is kept.
+func removeStrings(list []string, remove map[string]bool) []string {
+
+	var result = make([]string, 0, len(list))
+
+	for _, s := range list {
+		if !remove[s] {
+			result = append(result, s)
+		}
+	}
+
+	return result
+}
+
 // Binary
 func readByteFromFile(file string) (content []byte, err error) {
 
@@ -246,7 +272,48 @@ func readByteFromFile(file string) (content []byte, err error) {
 func writeByteToFile(file string, data []byte) (err error) {
 
 	var filename = getPlatformFile(file)
-	err = os.WriteFile(filename, data, 0644)
+	err = writeFileAtomic(filename, data, 0644)
+
+	return
+}
+
+// writeFileAtomic : Writes data to a temporary file in the target directory,
+// fsyncs it and renames it over name, so readers (and a crash mid-write)
+// never see a truncated or half-written file. The temp file is removed on
+// any error.
+func writeFileAtomic(name string, data []byte, perm os.FileMode) (err error) {
+
+	tmp, err := os.CreateTemp(filepath.Dir(name), ".tmp-*")
+	if err != nil {
+		return
+	}
+
+	var tmpName = tmp.Name()
+
+	defer func() {
+		if err != nil {
+			tmp.Close()
+			os.Remove(tmpName)
+		}
+	}()
+
+	if _, err = tmp.Write(data); err != nil {
+		return
+	}
+
+	if err = tmp.Sync(); err != nil {
+		return
+	}
+
+	if err = tmp.Close(); err != nil {
+		return
+	}
+
+	if err = os.Chmod(tmpName, perm); err != nil {
+		return
+	}
+
+	err = os.Rename(tmpName, name)
 
 	return
 }
diff --git a/src/toolchain_test.go b/src/toolchain_test.go
new file mode 100644
index 0000000..4deddc4
--- /dev/null
+++ b/src/toolchain_test.go
@@ -0,0 +1,86 @@
+package src
+
+import (
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+func TestWriteFileAtomic(t *testing.T) {
+	dir := t.TempDir()
+	file := filepath.Join(dir, "settings.json")
+
+	if err := writeFileAtomic(file, []byte("first"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	if err := writeFileAtomic(file, []byte("second"), 0600); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := os.ReadFile(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "second" {
+		t.Errorf("content = %q, want %q", got, "second")
+	}
+
+	fi, err := os.Stat(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fi.Mode().Perm() != 0600 {
+		t.Errorf("mode = %o, want 0600", fi.Mode().Perm())
+	}
+
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, e := range entries {
+		if e.Name() != "settings.json" {
+			t.Errorf("unexpected leftover file %q", e.Name())
+		}
+	}
+}
+
+func TestWriteFileAtomicMissingDir(t *testing.T) {
+	file := filepath.Join(t.TempDir(), "missing", "settings.json")
+	if err := writeFileAtomic(file, []byte("x"), 0644); err == nil {
+		t.Fatal("expected an error for a missing directory")
+	}
+}
+
+func TestRemoveStrings(t *testing.T) {
+	list := []string{"a.xml", "b.xml", "c.xml", "d.xml"}
+	got := removeStrings(list, map[string]bool{"b.xml": true, "d.xml": true})
+	want := []string{"a.xml", "c.xml"}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("removeStrings = %v, want %v", got, want)
+	}
+
+	// Nothing to remove: same content, original untouched.
+	got = removeStrings(list, nil)
+	if !reflect.DeepEqual(got, list) {
+		t.Errorf("removeStrings(nil) = %v, want %v", got, list)
+	}
+}
+
+func TestToFloat64(t *testing.T) {
+	cases := []struct {
+		in   any
+		want float64
+	}{
+		{float64(3), 3},
+		{int(2), 2},
+		{int64(1), 1},
+		{"x", 0},
+		{nil, 0},
+	}
+	for _, c := range cases {
+		if got := toFloat64(c.in); got != c.want {
+			t.Errorf("toFloat64(%v) = %v, want %v", c.in, got, c.want)
+		}
+	}
+}
diff --git a/src/webserver.go b/src/webserver.go
index 65bab81..a302603 100644
--- a/src/webserver.go
+++ b/src/webserver.go
@@ -9,6 +9,7 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"xteve/src/internal/authentication"
 
@@ -73,7 +74,17 @@ func StartWebserver() (err error) {
 
 	}
 
-	if err = http.ListenAndServe(":"+port, nil); err != nil {
+	// No ReadTimeout / WriteTimeout on purpose: /stream/ responses are
+	// long-lived. ReadHeaderTimeout still protects against slowloris
+	// clients and IdleTimeout reaps keep-alive connections.
+	var server = &http.Server{
+		Addr:              ":" + port,
+		Handler:           nil,
+		ReadHeaderTimeout: 15 * time.Second,
+		IdleTimeout:       120 * time.Second,
+	}
+
+	if err = server.ListenAndServe(); err != nil {
 		ShowError(err, 1001)
 		return
 	}
@@ -317,10 +328,6 @@ func DataImages(w http.ResponseWriter, r *http.Request) {
 // WS : Web Sockets /ws/
 func WS(w http.ResponseWriter, r *http.Request) {
 
-	var request RequestStruct
-	var response ResponseStruct
-	response.Status = true
-
 	var newToken string
 
 	/*
@@ -341,6 +348,12 @@ func WS(w http.ResponseWriter, r *http.Request) {
 
 	for {
 
+		// Fresh structs per command: a failed command must not leak its
+		// Status / Error / Base64 into the next one on the same connection.
+		var request RequestStruct
+		var response ResponseStruct
+		response.Status = true
+
 		err = conn.ReadJSON(&request)
 
 		if err != nil {
@@ -465,9 +478,7 @@ func WS(w http.ResponseWriter, r *http.Request) {
 			}
 
 		case "resetLogs":
-			WebScreenLog.Log = make([]string, 0)
-			WebScreenLog.Errors = 0
-			WebScreenLog.Warnings = 0
+			resetWebScreenLog()
 			response.OpenMenu = strconv.Itoa(indexOfString("log", System.WEB.Menu))
 
 		case "xteveBackup":
@@ -478,9 +489,7 @@ func WS(w http.ResponseWriter, r *http.Request) {
 			}
 
 		case "xteveRestore":
-			WebScreenLog.Log = make([]string, 0)
-			WebScreenLog.Errors = 0
-			WebScreenLog.Warnings = 0
+			resetWebScreenLog()
 
 			if len(request.Base64) > 0 {
 
@@ -855,8 +864,8 @@ func API(w http.ResponseWriter, r *http.Request) {
 
 		default:
 			token, err = tokenAuthentication(request.Token)
-			fmt.Println(err)
 			if err != nil {
+				ShowError(err, 0)
 				responseAPIError(err)
 				return
 			}
@@ -926,6 +935,7 @@ func API(w http.ResponseWriter, r *http.Request) {
 
 	if err != nil {
 		responseAPIError(err)
+		return
 	}
 
 	w.Write([]byte(mapToJSON(response)))
@@ -977,10 +987,10 @@ func setDefaultResponseData(response ResponseStruct, data bool) (defaults Respon
 	defaults.ClientInfo.OS = System.OS
 	defaults.ClientInfo.Streams = fmt.Sprintf("%d / %d", len(Data.Streams.Active), len(Data.Streams.All))
 	defaults.ClientInfo.UUID = Settings.UUID
-	defaults.ClientInfo.Errors = WebScreenLog.Errors
-	defaults.ClientInfo.Warnings = WebScreenLog.Warnings
-	defaults.Notification = System.Notification
-	defaults.Log = WebScreenLog
+	defaults.Log = webScreenLogSnapshot()
+	defaults.ClientInfo.Errors = defaults.Log.Errors
+	defaults.ClientInfo.Warnings = defaults.Log.Warnings
+	defaults.Notification = notificationsSnapshot()
 
 	switch System.Branch {
 
diff --git a/src/xepg.go b/src/xepg.go
index ccdffeb..8d40ce6 100644
--- a/src/xepg.go
+++ b/src/xepg.go
@@ -172,6 +172,11 @@ func createXEPGMapping() {
 
 	if len(Data.XMLTV.Files) > 0 {
 
+		// Files that could not be read are collected here and removed after
+		// the loop; mutating Data.XMLTV.Files while iterating over it used
+		// to duplicate entries instead of removing them.
+		var failedFiles = make(map[string]bool)
+
 		for i := len(Data.XMLTV.Files) - 1; i >= 0; i-- {
 
 			var file = Data.XMLTV.Files[i]
@@ -185,7 +190,7 @@ func createXEPGMapping() {
 
 			err = getLocalXMLTV(file, &xmltv)
 			if err != nil {
-				Data.XMLTV.Files = append(Data.XMLTV.Files, Data.XMLTV.Files[i+1:]...)
+				failedFiles[file] = true
 				var errMsg = err.Error()
 				err = errors.New(getProviderParameter(fileID, "xmltv", "name") + ": " + errMsg)
 				ShowError(err, 000)
@@ -215,6 +220,7 @@ func createXEPGMapping() {
 
 		}
 
+		Data.XMLTV.Files = removeStrings(Data.XMLTV.Files, failedFiles)
 		Data.XMLTV.Mapping = tmpMap
 
 	} else {
diff --git a/xteve.go b/xteve.go
index 6b28c62..3877b93 100644
--- a/xteve.go
+++ b/xteve.go
@@ -9,9 +9,11 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"runtime"
 	"strings"
+	"syscall"
 
 	"xteve/src"
 )
@@ -111,7 +113,7 @@ func main() {
 		err := src.Init()
 		if err != nil {
 			src.ShowError(err, 0)
-			os.Exit(0)
+			os.Exit(1)
 		}
 
 		src.ShowSystemInfo()
@@ -150,12 +152,13 @@ func main() {
 		err := src.Init()
 		if err != nil {
 			src.ShowError(err, 0)
-			os.Exit(0)
+			os.Exit(1)
 		}
 
 		err = src.XteveRestoreFromCLI(*restore)
 		if err != nil {
 			src.ShowError(err, 0)
+			os.Exit(1)
 		}
 
 		os.Exit(0)
@@ -164,25 +167,35 @@ func main() {
 	err := src.Init()
 	if err != nil {
 		src.ShowError(err, 0)
-		os.Exit(0)
+		os.Exit(1)
 	}
 
 	err = src.StartSystem(false)
 	if err != nil {
 		src.ShowError(err, 0)
-		os.Exit(0)
+		os.Exit(1)
 	}
 
+	// Graceful stop on SIGINT / SIGTERM: say goodbye on the network (SSDP)
+	// and exit cleanly instead of letting the runtime kill the process.
+	go func() {
+		quit := make(chan os.Signal, 1)
+		signal.Notify(quit, os.Interrupt, syscall.SIGTERM)
+		<-quit
+		src.Shutdown()
+		os.Exit(0)
+	}()
+
 	err = src.InitMaintenance()
 	if err != nil {
 		src.ShowError(err, 0)
-		os.Exit(0)
+		os.Exit(1)
 	}
 
 	err = src.StartWebserver()
 	if err != nil {
 		src.ShowError(err, 0)
-		os.Exit(0)
+		os.Exit(1)
 	}
 
 }