VTT subtitles are not displayed properly and impact subtitle size globally

[usrnammit]

Playing a video with subtitles in WEBVTT format will have it's subtitles rendered improperly (small font, large padding between lines). After playing VTT subtitles once, this same will happen to SRT subtitles too even if they were working fine before.

After observing this on my day-to-day Jellyfin instance I created a clean one.

v10.9.3, all default settings, one movie with SRT subtitles, one show with VTT subtitles.


1. Playing the movie with SRT - subtitles are rendered properly.




2. Playing the show with VTT - subtitles are small and overly spaced out (no settings were changed)




3. Playing the same movie as in step one - subtitles are now also too small and spaced out (again no change in settings)




Subtitles settings don't seem to have any impact, subtitles remain small even on the largest size setting. Clearing browser cache doesn't seem to help. Issue is user specific - a different user will see their subtitles fine (until they play a VTT themselves). Screenshots were taken in windowed mode, but window size had no impact when testing. The same VTT file worked fine in v10.8.13.

I have not found a way to reverse this behavior yet. Even if there isn't a fix for VTT, is there something I can do to get everything else to look normally again?

Logs from the test server
https://hastebin.com/share/uxepasovan.swift
https://hastebin.com/share/uxofozivik.csharp
https://hastebin.com/share/zedejusage.csharp

EDIT: Maybe I wasn't clearing browser data properly because I eventually managed to make it go away. But it still comes back any time I play a file with VTT subs.