SOLVED: Error after full disk: The input does not contain any JSON tokens.

[TheDreadPirate]

In this case it looks like it is trying to read the json for one of your plugins. Which tells me that a significant number of Jellyfin related files are corrupt now. You can try deleting most of your files except for your databases and the folder containing your library root configs, but you will likely need to start over.

Make regular backups, keep your media storage on a separate disk or partition from the jellyfin app data.