Plex doesn't choose subtitles itself anymore

[OttoKerner]

Managed user account can't set subtitles and audio language

The bug has been found. The fix is now in the release pipeline and should find its way into one of the next server releases. Until then, possible workarounds are: downgrade to plex server 1.16 , set the language prefs again, then upgrade again. edit the plex database directly as shown in here: How-to Guide: Setting default language for audio track & subtitles on managed accounts (e.g. Guest)