This is a weird one….I have at least two movies that only play when debug logs are enabled 
I’m using Emby as my backend and I know the files themselves are fine since I can play them both in Emby and Plex without issue. Without debug logging enabled, I get “this file can’t be played”, but to my surprise the video played without issue when I turned on debug logging to see what the problem was, I disabled debug logging and the files no longer played! 
This one is really confusing because how does the verbosity of the log file affect whether or not a file can be played? Here’s a debug log showing that the file plays when debug is enabled, then I stop it and it doesn’t play, then I turn it back on and it plays!