It sounds like an issue I had a while back. Finally solved: Movies stopping in direct play after exactly 2 hours
Solution
So the solution. All that needs to be done is that one single default variable needs to be changed and it’s super easy. All you need to do is change/add the TranscoderDefaultDuration variable in the hidden server settings to however many minutes you want and that’s that. By default it’s 120 (minutes), hence the 2 hour cut out. You can follow the link here on how to change it for your specifications: https://support.plex.tv/articles/201105343-advanced-hidden-server-settings/
