Are you sure the client and the server are powerful enough? Do they support all required codecs? I have issues with 4k movies because my Jellyfin is served by a

Are you sure the client and the server are powerful enough? Do they support all required codecs? I have issues with 4k movies because my Jellyfin is served by a mac mini, and my client is an old Android tablet that doesn't support hardware decoding, but that is hardly Jellyfin's fault. Though they just updated ffmpeg to the latest version, so it might help.