I was able to reproduce this bug on Xubuntu 20.04.4 LTS. But disabling xfce4-power-manager and removing the Power Manager plugin didn't work. Also as the "evtest" still receives mouse events (in a xfc4-terminal), it looks more like a problem in lightdm, xfwm4, or X11 server itself.
Is there a way to restart the WM without losing the X11 windows of all running applications? Or is there something I could test to give you more information? (e.g. running a debug/verbose version of xfwm4/lightdm)
I was able to reproduce this bug on Xubuntu 20.04.4 LTS. But disabling xfce4-power-manager and removing the Power Manager plugin didn't work. Also as the "evtest" still receives mouse events (in a xfc4-terminal), it looks more like a problem in lightdm, xfwm4, or X11 server itself.
Is there a way to restart the WM without losing the X11 windows of all running applications? Or is there something I could test to give you more information? (e.g. running a debug/verbose version of xfwm4/lightdm)