Thanks, Tapio and Menion.
First, in short: the problem is solved.
I didn't have a backup, and the problem persisted even after selecting a different dashboard.
"Run as service" was not turned on, in fact, I revoked all visible permissions and the deletion still failed - but that's no longer a problem at all.
However, during the search I found the menu item "Settings/Miscellaneous/Reset preferences", deleted the settings - and everything works, without error messages. Repeating the settings is of course not a problem.
Thanks for the ideas!
First, in short: the problem is solved.
I didn't have a backup, and the problem persisted even after selecting a different dashboard.
"Run as service" was not turned on, in fact, I revoked all visible permissions and the deletion still failed - but that's no longer a problem at all.
However, during the search I found the menu item "Settings/Miscellaneous/Reset preferences", deleted the settings - and everything works, without error messages. Repeating the settings is of course not a problem.
Thanks for the ideas!