Jellyfin server errors frequently reset the ZBR

[qrkourier]

Some requests via ZBR like POST /media/Sessions/Capabilities/Full get a server error (500), but only through browZer. The server error seems to trigger the ZBR to re-bootstrap, but it doesn't fix whatever the problem is.

Here's a normal request body and response when not using browZer.

{
  "PlayableMediaTypes": [
    "Audio",
    "Video"
  ],
  "SupportedCommands": [
    "MoveUp",
    "MoveDown",
    "MoveLeft",
    "MoveRight",
    "PageUp",
    "PageDown",
    "PreviousLetter",
    "NextLetter",
    "ToggleOsd",
    "ToggleContextMenu",
    "Select",
    "Back",
    "SendKey",
    "SendString",
    "GoHome",
    "GoToSettings",
    "VolumeUp",
    "VolumeDown",
    "Mute",
    "Unmute",
    "ToggleMute",
    "SetVolume",
    "SetAudioStreamIndex",
    "SetSubtitleStreamIndex",
    "DisplayContent",
    "GoToSearch",
    "DisplayMessage",
    "SetRepeatMode",
    "SetShuffleQueue",
    "ChannelUp",
    "ChannelDown",
    "PlayMediaSource",
    "PlayTrailers"
  ],
  "SupportsPersistentIdentifier": false,
  "SupportsMediaControl": true
}

Response

HTTP/1.1 204 No Content
Access-Control-Allow-Origin: *
Date: Sun, 28 Jul 2024 19:16:56 GMT
Server: Kestrel
X-Response-Time-Ms: 2.5558

[qrkourier]

I verified the request body is identical when it is part of a browZer or non-browZer session.

[qrkourier]

The POST request is initiated by the Jellyfin Service worker when not running in browZer, and by the ZBR instead of serviceworker.js when running in browZer.

Here's another example of a request that fails only in browZer. This one doesn't correspond with the ZBR re-bootstrapping itself the same way the other request did above.

POST /media/Sessions/Playing/Progress

{
  "VolumeLevel": 100,
  "IsMuted": false,
  "IsPaused": true,
  "RepeatMode": "RepeatNone",
  "ShuffleMode": "Sorted",
  "MaxStreamingBitrate": 1500000,
  "PositionTicks": 0,
  "PlaybackStartTimeTicks": 17221955326070000,
  "PlaybackRate": 1,
  "SecondarySubtitleStreamIndex": -1,
  "AudioStreamIndex": 1,
  "BufferedRanges": [],
  "PlayMethod": "Transcode",
  "PlaySessionId": "192a273e0c5a41a4b2d3bfdd2d93e96e",
  "PlaylistItemId": "playlistItem0",
  "MediaSourceId": "96a707bcf82206e68547b1bd2447a98a",
  "CanSeek": true,
  "ItemId": "96a707bcf82206e68547b1bd2447a98a",
  "EventName": "timeupdate"
}

When I visit Jellyfin in browZer and click on a media library the ZBR immediately re-bootstrapps, corresponding with but perhaps not caused by the server error response to POST /media/Sessions/Capabilities/Full.

If I attempt to play a video without first clicking on a library, such as one of the "recently added" titles, then I encounter the error response to POST /media/Sessions/Playing/Progress and the title does not play. The symptom is the thumbnail is displayed for a long time. In rare cases I was able to watch a few seconds of the title before ZBR re-bootstraps.