Fatal Playback error

[ACE]

Hi 

Jellyfin novice here.

I managed to install jellyfin on my ugreen nas using docker. Added media and got some of it working streaming to my TV, but there are many items that dont work on the TV get the "fatal playback error" on the desktop in firefox

All of the folders have a read/write permission and from what i have read there must be a transcoding error? 

Here is an example from my logs (i have no idea what any of this means   )

[2025-10-04 12:54:26.006 +00:00] [INF] [21] MediaBrowser.MediaEncoding.Transcoding.TranscodeManager: Deleting partial stream file(s) "/config/cache/transcodes/3bb879e0e2c7db210a954359a53b29f7.m3u8"
[2025-10-04 12:54:27.509 +00:00] [INF] [21] Emby.Server.Implementations.Session.SessionManager: Playback stopped reported by app "Jellyfin Web" "10.10.7" playing "Period One: The Appalling Mr Gormsby". Stopped at "0" ms
[2025-10-04 12:54:27.539 +00:00] [INF] [4] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: Playback stop tracker found, processing stop : "TW96aWxsYS81LjAgKFdpbmRvd3MgTlQgMTAuMDsgV2luNjQ7IHg2NDsgcnY6MTQzLjApIEdlY2tvLzIwMTAwMTAxIEZpcmVmb3gvMTQzLjB8MTc1OTU4MjQ0NDU5OQ11-3976af52a3ba47c9b2075c9b94d3da5b-66f1494bf1a93a4448f072f6727cf122"
[2025-10-04 12:54:27.540 +00:00] [INF] [4] Jellyfin.Plugin.PlaybackReporting.Data.PlaybackTracker: PlaybackTracker : Adding Stop Event : 10/04/2025 12:54:27
[2025-10-04 12:54:27.540 +00:00] [INF] [4] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: Playback stop but TrackedPlaybackInfo not found! not storing activity in DB
[2025-10-04 12:54:45.511 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: session.RemoteEndPoint : "192.168.1.243"
[2025-10-04 12:54:45.511 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : event_playing_id    = "66f1494bf1a93a4448f072f6727cf122"
[2025-10-04 12:54:45.512 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : event_user_id        = "3976af52a3ba47c9b2075c9b94d3da5b"
[2025-10-04 12:54:45.512 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : event_user_id_int    = 1
[2025-10-04 12:54:45.512 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : session_playing_id  = ""
[2025-10-04 12:54:45.512 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : session_user_id      = "3976af52a3ba47c9b2075c9b94d3da5b"
[2025-10-04 12:54:45.513 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : play_method          = "na"
[2025-10-04 12:54:45.513 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : e.ClientName        = "Jellyfin Web"
[2025-10-04 12:54:45.513 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : e.DeviceName        = "Firefox"
[2025-10-04 12:54:45.513 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : ItemName            = "Seven Periods With Mr. Gormsby - s01e01 - Period One: The Appalling Mr Gormsby"
[2025-10-04 12:54:45.513 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : ItemId              = "66f1494bf1a93a4448f072f6727cf122"
[2025-10-04 12:54:45.514 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : ItemType            = "Episode"
[2025-10-04 12:54:45.514 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : Details do not match for play item
[2025-10-04 12:54:45.514 +00:00] [INF] [18] Jellyfin.Plugin.PlaybackReporting.EventMonitorEntryPoint: StartPlaybackTimer : Exited

Any help would be welcomed as this is my first time doing any of this im a windows user only with no code or anything of the like experience!

Thanks

[ACE]

Didnt get any response here so I will just update in case any other newbie like me has a similar issue

I could only get 50% of my media to play. I checked everything over endlessly but nothing fixed the problem.

Basically since i was my first time using anything like this i followed a youtube video on how to set jellyfin up on docker, in the video they missed the key step of ticking the graphics card performance box when creating a container from an image. Quite easy to miss if you have never setup anything before.

I deleted jellyfin reinstalled doing that and set it up as i had before and now everything transcodes rpoerly and I can play all of my media!