Update: It specifically happens to part2; part1 can still be played, but it gives the h4 error every time you try to have it play part2 normally until Plex Server and/or PC reboot.
I do plan to use MKVToolNixGUI to merge the parts, which I hope will prevent this! But I shouldn’t have to: it’s the same H264 codec for both part1 and part2!
