When using CTRL+ALT+Fx to switch to other user, I often receive a modal popup for which I do not own a password.
Who is “Sicer”? That could be the clue to your solution
Slicer is just the user I currently switched to, but this happens with any other
What happens when you supply “Slicer”'s password?
Sir, … the screen shows that it is Slicer’s password that is required (no other user’s password)
It was Slicer’s password sir! …otherwise it would not be an issue (although annoying, I see no reason for these updates to be authenticated manually)
Perhaps you need to file a bug report against pam or polkit at https://bugzilla.redhat.com
OR
You haven’t quite explained the problem to my comprehension