The server caches your device ID at some point I believe, although I’m not a jellyfin developer so you’d need to look into their documentation for confirmation if you don’t already know yourself.

🤔 it’s probably something cache related or due to a clock offset then. Beyond that I’m not sure what I would investigate.

So there’s a change regarding reverse proxies in one of the recent updates that requires you to specify the approved ip of the reverse proxy. Are you using one? If so, it could be this.