The two issues I had over the years was: My SSL cert expiring (not really a Jellyfin issue).
My FireTV updated the Jellyfun app to a version that no longer supported the server version, this was pretty frustrating becuase I just wanted to sit down and watch some TV instead of messing around with a upgrade.
In saying that; Kodi also ran fine for years without issue. My main issues with Jellyfin are scrubbing difficulties and subtitles going out of sync or not being able to change their timings, same with audio timings.