I've got an open media vault nas over the weekend with raspberry pi 3b + tinkered on it now runs plex.
Plex works well too (on the TV, laptop) but when I look at the mobile app (android) then playback starts, but at some point (always in the same place) I come back to the menu of the movie… (this happens with all movies and if you continue to play the movie goes on for 2 minutes and then the same happens again…
I've already ruled out a few mistakes
The Mp4 on the ssd of the Raspberry pi is playable without this bug…
Everything works fine on other Plex devices…
And start again (plex and raspberry pi I already have).
Does somebody has any idea?
I have browsed online for quite a long time and found nothing.
I have looked in the Google PlayStore in the reviews. The Android APP from Plex seems to be quite buggy. Maybe that's the problem with you too. Since the problems appear only on your Android device so that sounds at least likely.
As far as I know you could possibly try to change the streaming setting for your phone on the Plexserver. There you can probably set the resolution in the videos to the individual clients. Perhaps you can achieve something with it. It may also be that your Raspi convert the video to stream to your smartphone. This can be a fairly compute-intensive process that may overwhelm the Raspi.
