I finally figured out my issue so hopefully this helps you as well.
I turned on network logging for my plex client (fire tv stick):
https://support.plex.tv/articles/201573117-android-android-tv-fire-tv-logs/
I found some logs that pointed to exoplayer crashing with an out of bounds exception. Googled it and found this incredibly long thread:
TL;DR: The integrated video player for android based plex clients uses an older version of exoplayer. This version has a known bug where subtitles can sometimes cause it to crash randomly if they aren’t synced with the video correctly.
WORKAROUND:
Turn off subtitles when you try and play the episode. If you need subtitles then still turn them off, let the episode play for about 15 seconds, then turn them back on.
Hopefully this helps!
