Turning off one monitor moves all windows to second monitor

[Shinbobikal]

I installed a fresh and updated Linux Mint 20 Cinnamon and noticed that when I turn off my monitor (1920x1080), which is connected via DisplayPort (Graphics card + monitor), all windows are moved to my second monitor (1366x768, card: DisplayPort -> monitor: VGA).
This doesn't happen the other way around (turning off other screen), even when changing the "main monitor" setting.
Changing the virtual xserver-location of the screens also doesn't change anything (it's not the common "all windows on first screen" problem).

This would somehow be expected if the second monitor would be turned on, but it's off.

On Ubuntu 19.10 and I think Mint 19 this didn't happen and I'd like the windows to stay where they are if I turn off my monitor.

Edit: When the screensaver starts or the system is locked the windows aren't moved.

Code: Select all

Graphics:
  Device-1: AMD Navi 10 [Radeon RX 5600 OEM/5600 XT / 5700/5700 XT] 
  vendor: Tul driver: amdgpu v: kernel bus ID: 2b:00.0 chip ID: 1002:731f 
  Display: x11 server: X.Org 1.20.8 driver: amdgpu,ati 
  unloaded: fbdev,modesetting,radeon,vesa resolution: 1366x768~60Hz 
  OpenGL: renderer: AMD Radeon RX 5700 XT (NAVI10 DRM 3.35.0 
  5.4.0-40-generic LLVM 10.0.0) 
  v: 4.6 Mesa 20.0.8 direct render: Yes

Any ideas?

[Shinbobikal]

Don't know if that's the same root course, but when the windows are moved, the background image on the main monitor is cropped to the size of the second monitor and the remaining space is black.