do not preload captions

assets/js/player.js

@@ -21,6 +21,7 @@ var options = {
         ]
     },
     html5: {
+        preloadTextTracks: false,
         hls: {
             overrideNative: true
         }
@@ -547,3 +548,10 @@ window.addEventListener('keydown', e => {
 if (player.share) {
     player.share(shareOptions);
 }
+
+// show the preferred caption by default
+if (player_data.preferred_caption_found) {
+    player.ready(() => {
+        player.textTracks()[1].mode = 'showing';
+    });
+}