Cinnamon CPU usage reaches 100% after lock screen

Distribution

Linux Mint 21.1 Cinnamon Desktop

Package version

5.6.8

Graphics hardware in use

None

Frequency

Always

Bug description

Recently I have converted my Laptop to a Proxmox server and I am running Linux Mint Cinnamon in a container. When the screen is unlocked and no specific application is running, the CPU usage is 2-5%. As soon as lock the screen it reaches 96-98% even though I am not running any application. Once I unlock the screen again it goes down to 2-5%.

This issue is replicable only in Linux Mint Cinnamon Desktop. Linux Mint XFCE Desktop works fine.

I have provided more details about the system in this forum https://forums.linuxmint.com/viewtopic.php?p=2348954

Steps to reproduce

1. Install Proxmox on a desktop.
2. Install Linux Mint Cinnamon OS in a VM and update it.
3. Log in to the system and the lock the screen.

Expected behavior

The CPU usage should be similar for both Locked and Unlocked screen.

Additional information

https://forums.linuxmint.com/viewtopic.php?p=2348954

*mtwebster - edit: fixed forum links

No source files, tests, or entry points are named. First reproduce the issue in the described Linux Mint Cinnamon setup, compare CPU usage while locked and unlocked, and use the linked forum report for additional system details; done means lock-screen CPU usage remains comparable to the unlocked state.