The next episode starts without the wait
Pressing the next-episode card asked every one of your addons from scratch, so the
source list you had been looking at a minute earlier was rebuilt while you waited.
Nuvio now fetches them quietly two minutes before the episode ends, and the card
plays from what it already has. Réglages → Lecture → Épisode suivant → Précharger
l'épisode suivant, on by default.
A refresh still goes out to the addons — asking for the list again means asking for
a fresh one.
Playback errors say what to do about it
When the MPV engine gave up it printed its own words: "unrecognized file format" and
similar. True, in English, and no help at all.
It now says which of three things happened — the source sent something unplayable,
the file needs a decoder this engine does not have, or it never opened — and what is
worth trying next. mpv's own text is still underneath, for when you want to tell
someone about it.