I have multiple multi-part videos and not a single one will play anything but the first part.
Most recently have the following 2 files:
Lord of the Rings/Lord of the Rings - The Fellowship of the Ring, Part 1.mp4
Lord of the Rings/Lord of the Rings - The Fellowship of the Ring, Part 2.mp4
Both appear in my plex server stacked properly.
The movie reports the full length is the length combined on the 2 clips.
This lengths is properly reflected in the Apple TV Client
When the first part ends, the playback ends.
If I go back into it, I get a dark screen with a "no" circle flashing in the lower left hand corner.
It then exits out to the end of movie screen.
No matter how many times I go back into it this is the result.
I experienced EXACTLY the same effect on multiple movies and tv shows, and I can get NONE to work as expected. I cannot watch my media as a result and am having to resort to using the original disks, completely deleting the purpose of using Plex in the first place.