Can it be related to screenlock ?
No. Screenlocking is disable as hybernation. Only screen energy saving is enable but I never got any issues with that before.
You mean even other consoles don't work, is it an X failure or total graphics failure?
It's hard to say if it was a total graphics failure, because the keyboard and mice was not responding anymore.
The leaner the better
Not totally agree of this philosophy. A GUI is supposed to works and not drive the rest of the peripheral with it and even better, in case of a crash the GUI should be able to restart automatically and recover the previous state.
https://www.youtube.com/watch?v=nqi7KlTl6Uc
It is not by changing ingredients ( xorg > wayland ) that we necessarily obtain a better dish, it may also be necessary to replace the chef.