Edit: whoops, just realized you said freezing not crashing, and probably have a separate issue. I'll leave this here in case it helps anyone that finds this thread with crashes a couple minutes into videos.
Had this issue ages ago, then my dad did too a year later on a different client version. Manually changing the "preferred media player" option fixed it on my firestick 4k, 4k Max, and my dads standard firestick.
Jellyfin app>settings menu>Playback>Video section>preferred media player>libVLC (in my case, Exoplayer seemed to be causing the crashes approx 2 years ago but you can try both, I just tried exoplayer again and it doesn't seem to be crashing either when set manually now so it may have been patched)
You joke but when "media" outlets boldly steal 90% of their content directly from reddit posts and comments without attribution for commercial use, maybe including a license isnt crazy anymore?