Hi Michael, thanks for the fast feedback.
I did "apt remove mate-polkit" followed by an "apt autoremove" to get rid of mate-polkit-common, accountservice was left installed. Rebooted the VM: auth is possible more than once now. Looks like your suspicion that the authentication agent might be missing is correct. I guess fixing the dependency between cinnamon and accountservice does the job. Regards, Rolf
