Hi - I have similar issues as Lakarin.
I even did the Plex dance a few times, but still the issue remains.
After copying the files/folders back into the library, the subtitles are available for a few seconds, - until the metadata crawl has finished, then the subtitles disappear in the player. ??
I have absolutely no clue what to do now. This feels like a bug, for sure.
But please help out.
Thanks
Synology NAS server, Plex Mac media player.
Latest PlexMediaServer-1.18.9.2578-513b381af-x86_64.spk
Filenames are renamed with FileBot, also latest version.
here are some screenshots






