diff --git a/src/components/playback/playbackmanager.js b/src/components/playback/playbackmanager.js
index f0cf735522..f6c366b7ae 100644
--- a/src/components/playback/playbackmanager.js
+++ b/src/components/playback/playbackmanager.js
@@ -876,15 +876,28 @@ class PlaybackManager {
             });
         };
 
-        self.hasSecondarySubtitleSupport = function (player = self._currentPlayer) {
+        self.playerHasSecondarySubtitleSupport = function (player = self._currentPlayer) {
             if (!player) return false;
             return Boolean(player.supports('SecondarySubtitles'));
         };
 
+        /**
+         * Checks if:
+         * - the track can be used directly as a secondary subtitle
+         * - or if it can be paired with a secondary subtitle when used as a primary subtitle
+         */
+        self.trackHasSecondarySubtitleSupport = function (track, player = self._currentPlayer) {
+            if (!player || !self.playerHasSecondarySubtitleSupport(player)) return false;
+            const format = (track.Codec || '').toLowerCase();
+            // Currently, only non-SSA/non-ASS external subtitles are supported.
+            // Showing secondary subtitles does not work with any SSA/ASS subtitle combinations because
+            // of the complexity of how they are rendered and the risk of the subtitles overlapping
+            return format !== 'ssa' && format !== 'ass' && getDeliveryMethod(track) === 'External';
+        };
+
         self.secondarySubtitleTracks = function (player = self._currentPlayer) {
             const streams = self.subtitleTracks(player);
-            // Currently, only External subtitles are supported
-            return streams.filter((stream) => getDeliveryMethod(stream) === 'External');
+            return streams.filter((stream) => self.trackHasSecondarySubtitleSupport(stream, player));
         };
 
         function getCurrentSubtitleStream(player) {
@@ -1575,7 +1588,7 @@ class PlaybackManager {
 
         self.setSecondarySubtitleStreamIndex = function (index, player) {
             player = player || self._currentPlayer;
-            if (!self.hasSecondarySubtitleSupport(player)) return;
+            if (!self.playerHasSecondarySubtitleSupport(player)) return;
             if (player && !enableLocalPlaylistManagement(player)) {
                 try {
                     return player.setSecondarySubtitleStreamIndex(index);
diff --git a/src/controllers/playback/video/index.js b/src/controllers/playback/video/index.js
index dfbf714c7a..84e7a8d719 100644
--- a/src/controllers/playback/video/index.js
+++ b/src/controllers/playback/video/index.js
@@ -990,7 +990,7 @@ import { setBackdropTransparency, TRANSPARENCY_LEVEL } from '../../../components
 
         function showSecondarySubtitlesMenu(actionsheet, positionTo) {
             const player = currentPlayer;
-            if (!playbackManager.hasSecondarySubtitleSupport(player)) return;
+            if (!playbackManager.playerHasSecondarySubtitleSupport(player)) return;
             let currentIndex = playbackManager.getSecondarySubtitleStreamIndex(player);
             const streams = playbackManager.secondarySubtitleTracks(player);
 
@@ -1071,7 +1071,7 @@ import { setBackdropTransparency, TRANSPARENCY_LEVEL } from '../../../components
              * - primary subtitle is `External`
              */
             if (
-                playbackManager.hasSecondarySubtitleSupport(player) &&
+                playbackManager.playerHasSecondarySubtitleSupport(player) &&
                 streams.length > 1 &&
                 secondaryStreams.length > 0 &&
                 currentIndex !== -1 &&
diff --git a/src/plugins/htmlVideoPlayer/plugin.js b/src/plugins/htmlVideoPlayer/plugin.js
index d00ff53d2c..c532bc95a4 100644
--- a/src/plugins/htmlVideoPlayer/plugin.js
+++ b/src/plugins/htmlVideoPlayer/plugin.js
@@ -478,9 +478,10 @@ function tryRemoveElement(elem) {
                 const initialSubtitleStream = options.mediaSource.MediaStreams[this.#subtitleTrackIndexToSetOnPlaying];
                 if (!initialSubtitleStream || initialSubtitleStream.DeliveryMethod === 'Encode') {
                     this.#subtitleTrackIndexToSetOnPlaying = -1;
+                    secondaryTrackValid = false;
                 }
-                // secondary track should not be shown if primary track is no longer `External` or is not on
-                if (initialSubtitleStream && initialSubtitleStream.DeliveryMethod !== 'External') {
+                // secondary track should not be shown if primary track is no longer a valid pair
+                if (initialSubtitleStream && !playbackManager.trackHasSecondarySubtitleSupport(initialSubtitleStream)) {
                     secondaryTrackValid = false;
                 }
             } else {