I think it happened after an update of the Host OS Ubuntu 20.04: A full screen VM display correctly. However each Host screen with a window is displayed with the last full screen Virtualbox VM. Last is the one with the highest number. I can get even 3 virtual desktops mixed in one screen, see screenshot.
** Attachment added: "Screenshot from 2020-03-25 02-58-43.png" https://bugs.launchpad.net/ubuntu/+source/meta-gnome3/+bug/1868926/+attachment/5341335/+files/Screenshot%20from%202020-03-25%2002-58-43.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1868926 Title: Host OS desktops get mixed in one screen To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/meta-gnome3/+bug/1868926/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs