cannot change spotify credentials

[nerdoc]

The current Spotify setting under /settings.php?p=features is not working after you set the spotify credentials. I am using Runeaudio e6 20201122, and recently updated the system via UI.
The spotify setting is enabled, and I can select the runeaudio device as playing device in my spotify app. But I want to change the user to another one. It is enabled:

But after a while, the spotify setting is switched off again - without my interaction - but the daemon in the background is still running.

This is weird - but the main problem is, that I can't change the spotify user...

● spotifyd.service - A spotify playing daemon
     Loaded: loaded (/usr/lib/systemd/system/spotifyd.service; enabled; vendor preset: disabled)
    Drop-In: /etc/systemd/system/spotifyd.service.d
             └─override.conf
     Active: active (running) since Tue 2020-11-24 21:08:23 CET; 41s ago
       Docs: https://github.com/Spotifyd/spotifyd
    Process: 3350 ExecStartPost=/srv/http/bash/cmd.sh nicespotify (code=exited, status=0/SUCCESS)
   Main PID: 3349 (spotifyd)
      Tasks: 4 (limit: 2139)
     CGroup: /system.slice/spotifyd.service
             └─3349 /usr/bin/spotifyd --no-daemon

Nov 24 21:08:23 runeaudio taskset[3349]: Using software volume controller.
Nov 24 21:08:23 runeaudio systemd[1]: Started A spotify playing daemon.
Nov 24 21:08:23 runeaudio taskset[3349]: Failed to register IPv6 receiver: Os { code: 97, kind: Other, message: "Address family not supported by protocol" }
Nov 24 21:08:29 runeaudio taskset[3349]: Connecting to AP "gew1-accesspoint-b-trmv.ap.spotify.com:443"
Nov 24 21:08:30 runeaudio taskset[3349]: Authenticated as "<snip>" !
Nov 24 21:08:30 runeaudio taskset[3349]: Country: "AT"
Nov 24 21:08:30 runeaudio taskset[3349]: Using alsa sink
Nov 24 21:08:30 runeaudio taskset[3349]: Loading  with Spotify URI 
Nov 24 21:08:31 runeaudio taskset[3349]:  loaded
Nov 24 21:08:31 runeaudio taskset[3349]: Running "/srv/http/bash/spotifyd.sh" using "/bin/bash" with environment variables {"TRACK_ID": "1300POeOaj8qho30FRHjgf", "PLAYER_EVENT": "stop"}