I'm getting FATAL: Keyboard error:995 as well in Vbox but not all the time... but yeah, more often than not.
I tried the Xfce ISO in the same conditions and it happens rarely with it... but it happens as well.
This is similar to the VMSVGA issue imo... whatever it is, it's not happening ALWAYS or NEVER depending on the ISO. It seems to happen now and then based on parameters we don't control and we don't understand. Until we know more about this, this is just a Vbox issue then.
Live booted -- gives errors in either "apt-get update" or e.g. opening "Driver Manager".
E: The repository 'cdrom://Linux Mint 19.3 _Tricia_ - Release amd64 20191213 bionig Release' does not have a Release file.
[and associationed warnings/Ign/Err that then occurs consequently].
Appear to have this booting in all 3 virtualbox virtual-graphics-device modes at least once, screen auto-resize does not work, but now functional installer WHEN booted ok.
HOWEVER, certainly installed system (and, I think, sometimes installer) can sometimes exhibit a black-screen scenario, from which ctrl+alt+backspace and then logging-in again, escapes-from. I am SUSPECTING there is a 'race-condition' with the timing of loading relevant vboxguest/vboxvideo modules...
shutter won't install in livecd prior to updating apt cache, missing package
hitting reboot after running integrity check:
FATAL: Keyboard error:995
is fine on real hardware