not OP, but this has reared its ugly face once or twice with my friends.
i have been running into another issue, though it may be a firefox issue: playing some filetypes fail to play on web browser but work fine on jellyfin app (i believe my settings are correct for hardware decode on server where it can)
i still have to put some time into figuring it out tho (havent really done my research yet)
This is one of my issue with Jellyfin. It's a workaround to install the app onto Tizen. Updates are again manual. But zero issues since installation and runs smooth.