Your logs show that your phone repeatedly cannot resolve your Jellyfin server’s Tailscale address while Symfonium is in the background. Connectivity returns when you reopen the app.
There is also a longer interruption while playing an already cached song, so the connection issue does not explain everything. Symfonium is currently not exempt from battery optimization.
Please disable battery optimization for both Symfonium and Tailscale, ensure background usage is allowed, and repeat playback with the screen off. Also try an explicitly offline-cached track to isolate playback from the server connection.
If it stops again, leave debug logging enabled, note the exact time, press Play once, and upload the logs immediately afterward. Please clarify whether the interface itself stops responding or only playback does.