Lock screen not displaying correctly on dual monitor setup with scaling.

[rmysliwczyk]

Distribution

Mint 22.1

Package version

6.4.7

Graphics hardware in use

AMD Radeon Rx 470

Frequency

Always

Bug description

Lock screen doesn't display properly (black screen with graphical glitches) when my main display (landscape) is set to 125% scaling, with my secondary (vertical) display is set to 100% scaling.

Steps to reproduce

Have main display scaling set to 125% and secondary display to 100%. Click on Lock screen button in the menu.
Here's a link to video showing my issue: Lock screen bug

Expected behavior

Lock screen displaying properly.

Additional information

The bug doesn't seem to appear when I set scaling to 150% on my main display and 100% on my secondary display. Also, occasionally when I unlock my screen (no matter if with 125% or 150% scaling) my wallpaper is zoomed in, but I've made a comment about this in linuxmint/cinnamon#12009. My main display is Samsung 29" 3840x2160 (16:9) in landscape. My secondary monitor is NEC 22" 1680x1050 (16:10) in vertical mode.

systeminfo.txt

[q6276270]

I've got a similar setup and the same problem. Since I know python fairly well I tried to debug the problem today for some time but couldn't pinpoint the location of the error in the python code.
It seems that the program uses GObjekt bindings to control some non-python code in the background which triggers the error message:

Screen rect (0,0-XxY) and 2 monitor rects (0,0-XxY) DO NOT add up, skipping change notification

when switching back to one screen it works again. Unfortunately I don't know how to dive any deeper. It might even be a bug in the gobject library instead of the screensaver https://gitlab.gnome.org/GNOME/pygobject
Also other messages indicate the same scaling factor of 2 is applied to both screens, even though my screen configuration is a scaling of 125% and 100% for the screens respectively.
Enabling interactive debugging breaks the lockscreen completely. The screen freezes except for the cursor and I cannot input anything anymore, not even unlock the screen it seems.