When switching users: prompt "Password required to make software changes" disables desktop

Distribution

Linux Mint 22.1

Package version

Cinnamon 6.4.8

Graphics hardware in use

AMD RX 6600

Frequency

Quite often

Bug description

I have two user accounts: Administrator and standard user accounts. The admin user is almost always logged in and the standard account is logged into from the lock screen while the admin account is still logged in.

When switching from the standard account to the admin account either by logging out or switching users from the Cinnamon menu or by pressing ctrl + alt + F7 the admin users desktop will be dimmed and inaccessible with a password prompt taking focus. The prompt says "Password required to make software changes" and will not accept any password nor can it be cancelled. The admin password does not work and the prompt gives an error and the cancel button doesn't do anything.

alt+F2 "r" does nothing and a TTY is not accessible either as ctrl+alt+[F1-F6] is unresponsive.

Steps to reproduce

• log in as administrator
• switch users to a different user
• wait 15,20,30 minutes
• switch back to administrator account

Expected behavior

The administrator should be able to log back in and use the desktop as normal.

Additional information

The issue seems to take some time to affect the administrator user. I do not have an exact time but it could be 15-30 minutes at least.

This does not seem to be related to #10570 but fits a general theme of issues with user switching on Cinnamon.

I have no idea what software changes are being made that provoke the system to require this password since it appears for a user currently not using the desktop.

Ways around the issue: You can still open the Cinnamon menu with the Super key and navigate it with the arrow keys even though it's very dim. Log out from the Cinnamon menu and log in again. You can also switch back to the other user from the Cinnamon menu this way. From the second users desktop a sudo killall --user <admin user> does the trick as well (remember a TTY is not accessible from the affected users desktop).

Start by reproducing on Linux Mint 22.1 with Cinnamon 6.4.8 using administrator and standard accounts, switching back after 15–30 minutes. No source file or test is identified, so trace the user-switching and password-prompt path; done means the administrator desktop returns normally without an uncancellable prompt.