Stream from NAS subtitles always freezes at 1:10/1:20 hour

I stream my videos from my QNAP NAS to my WeTek 2 mediaplayer. Every time at about 1 hour and 10 or 20 minutes the subtitles freezes and the Kodi menu can’t be reached. Than i need to go back to the main menu of the mediaplayer and restart Kodi. I checked the CPU and the work memory during the movie and its about 34% full, so that is not the problem.I had the same problem with a different android mediaplayer (which i returned). I am 100% sure Kodi is the problem because the other apps (Netflix) doesn’t have the problem. I also tried to watch the movie from my Playstation 4 and this works perfectly.
Does anyone has a clue?