Shutdown leads to LightDM screen

Distribution

Mint 22

Package version

6.2.9

Graphics hardware in use

Intel HD Graphics 2000 series

Frequency

Always

Bug description

When Automatic Updates are enabled in Update Manager, and if these automatic updates are running by triggering the time, system shut down will not work properly. It will seemingly shut down, giving me a black screen and then it will drop me onto the LightDM lock screen. The same login screen appears on boot up where I can insert my password, change my DE for the session, shut down etc. Whenever I want to shut down from within this login screen with the button in the top right corner, I get a shut down prompt, but there's no button to press where supposedly there should be buttons.

To be sure this was not a fluke, I restored a Timeshift backup from November 25th, before automatic updates had been done. Let my laptop sit for a while and plugged in the AC adapter. When I heard the HDD clearly being actively used, I also saw that the notification icon for the automatic updates was sitting in the bottom right corner. I then proceeded to try to shut down my laptop, and the same issue occurred just like it did before.

I have exported the full log of this reproduced bug and posted it here https://pastebin.com/8w9YiFtk. From 12:13 onward I try to shutdown the machine multiple times, and also try hibernate, which works just fine. A video of my troubleshooting from 12:13 onward can be found here: https://youtu.be/K1_vAyM3moA My system language is set to Dutch, so some text will appear in Dutch.

I retested this inside a clean VM multiple times, and the issue keeps occuring. Even when I retested it a week later today (December 15th).

Steps to reproduce

Do a clean install of Linux Mint Cinnamon 22 accepting the default settings
Change settings in Update Manager > Preferences > Automation > Apply updates automatically
Wait for update time to pass until Automatic Updates cogwheels icon is sitting in the notification area
Try shutting down using the Mint menu Menu > Quit > Shut Down
Observe that the system won't shut down but instead drops to the LightDM lock screen.

Expected behavior

Wait for update time to pass until Automatic Updates cogwheels icon is sitting in the notification area
Try shutting down using the Mint menu Menu > Quit > Shut Down

• See an error message showing that the system cannot shut down
• Or run updates on shut down
• Or cancel updates and shut down

Additional information

No response

Start by reproducing the failure using the listed Linux Mint Cinnamon 22 installation and automatic-update steps, then inspect the linked log and video around the shutdown attempts. Done means shutdown no longer returns to LightDM, or the system clearly reports, runs, or cancels pending updates instead.