For some reason whenever I watch certain TV shows it defaults to subtitles on. Each episode I need to go and disable. I can find places to force them ON but not OFF. I never had to to this before, and Ive been running plex for a very long time now.
Set Settings > Account > AUDIO & SUBTITLE SETTINGS > AUTO-SELECT SUBTITLE MODE to Manually Selected. That means, Plex will only show subtitles if you manually select them.
If your files only have a single audio track, you can also disable Automatically select audio and subtitle tracks.
Thank you