These tips are for Virtualbox (tested on version 6.0.4 of Virtualbox running on Debian 10.2 Stable host), especially targeted to somewhat experienced users who have successfully installed Virtualbox Guest Additions on their guest, for example those in the community who wish to build LFS on a VM. I am not sure if the same tips will be useful for Virtualbox running on other hosts.
I was finding that guests kept causing crashes due to erratic mouse behaviour as the mouse moved from guest to host or vice-versa, or even mouse pointer being lost within the guest itself, especially if guest was run full-screen without a bordering Virtualbox bordering window on the host. The mouse problems were occuring under Gnome, XFCE and KDE all on the same hardware and OS. After many, many hours, I’ve finally managed to reduce crashes to zero on my system!
The tips have been tested with the following guests: Debian 10.2 Stable, Fedora 31, Ubuntu 18.04.3 LTS.
Referring to settings window:
General: Advanced tab, disable Shared Clipboard, disable Drag’n’drop.
System: Motherboard tab, set Pointing Device to PS/2 Mouse, enable I/O APIC
Display: Screen tab, set Graphics Controller to VMSVGA, disable 3D Acceleration
Run the guest in a maximised Virtualbox window on the host not in full-screen mode
Hope that’s of some use