

Are you using wireless? I’m guessing your router is occasionally being oversaturated with traffic. I would turn your streaming quality down to around 2mb and then stream to your device. You can open up Jellyfin in a browser and check the steam information in the Jellyfin Dashboard to check the speed. Keep bumping it up if you want better quality.
If you’re trying to prevent transcoding, then I suggest downloading or ripping lower bitrate content.
If you happen to have a spare router, I would try adding it as an access point and keep your Jellyfin source machine and streaming device on that access point. That should keep the traffic from going through your primary router.
Are they Samsung TVs?