LightDM crashes when switching from another X session

[Rostislav Navrátil]

Steps to reproduce:
1) Boot into LightDM greeter (waiting for password for user1).
2) CTRL-ALT-F5 to switch to another console.
3) Log as user2. Start X by command: startx -- :1
4) CTRL-ALT-F7 to Switch to original console.
At this time I can see that LightDM is restarting and greeter shows me field for password for user1.

Another tests:
1) Boot into LightDM greeter (waiting for password for user1).
2) CTRL-ALT-F5 to switch to another console.
3) Log as user2. Start X by command: startx -- :1
4) CTRL-ALT-F6 to switch to another console.
5) Log as user1. Start X by command: startx -- :2
6) Switch between F5 and F6 consoles - everything works flawlessly.
7) CTRL-ALT-F5 to switch to console with user2.
8) CTRL-ALT-F7 to switch to console waiting for password for user 1 - LightDM is restarting almost always.
9) CTRL-ALT-F5 to switch to console with user1.
10) CTRL-ALT-F7 to switch to console waiting for password for user 1 - LightDM is OK sometimes.
* It looks as if switching between LightDM waiting for user1 password and X session with user2 makes LightDM crash often times than switching between LightDM waiting for user1 password and X session with the same user.
* When there is longer time (5 minutes) between switching between LightDM waiting for user1 password and X session with the same user, it crashes with high probability (maybe always).

My environment: Xubuntu 20.04 (upgraded from older versions), XFCE, processor AMD Ryzen 5 2400G.
$ sudo inxi -G
Graphics:
  Device-1: AMD Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series]
  driver: amdgpu v: kernel
  Display: server: X.Org 1.20.8 driver: amdgpu,ati
  unloaded: fbdev,modesetting,vesa resolution: 1920x1080~60Hz
  OpenGL: renderer: AMD RAVEN (DRM 3.35.0 5.4.45-050445-generic LLVM 10.0.0)

The same behaviour affects another computer with the same processor and Xubuntu 18.04, XFCE.

This behaviour is probably nothing new, it was also mentioned here:
https://lists.freedesktop.org/archives/lightdm/2017-September/001081.html

Can I add any other useful piece of information, result of some command etc?

[Rostislav Navrátil (signy13)]

Sorry for this bugreport, I was not aware that statx for running multiple session is not supposed to work under LightDM. Once I found command:
dm-tool switch-to-greeter
everything works and there is no need to use startx for running multiple users.