Do you think you could post a picture of the exact error message? Also you could check the Plex logs through the web app and you should see the exact error and what component caused it. If I had to take a guess, I’d say your uncompressed movie has something that’s causing the server to transcode (TrueHD audio or a forced HDMV subtitle stream) and the transcoding process is failing.
I know you’re right and that’s probably what the movie is but it would be a lot funnier if they instead just ripped off John Carpenter’s They Live. Put on the ViewMaster to see the truth kids!