Visual glitch in VirtualBox VM using resolutions with 768

The problem is that if i set resolution for my Ubuntu 18.10 VM (same with 18.04.1) to 1024x768 or 1280x768 some objects only appear on screen when hovering with mouse cursor. 800x600, 1280x800 work fine.
Xubuntu 18.10 works ok with 1024x768, as well as Fedora 29 which also uses Gnome. As i can’t get solution for this in VirtualBox forums, maybe someone here would have a hint.

More detailed information is in VirtualBox forums post: https://forums.virtualbox.org/viewtopic.php?f=3&t=91734

This site is for the co-ordination of the Ubuntu project(s), and not support.

For Ubuntu Support options, please have a look at https://community.ubuntu.com/t/finding-help/712 (though they won’t be able to help you if the problem is related to your windows host)

Sorry. I was originally going to community.ubuntu.com but after the registration and email validation it brought me here (discourse.ubuntu.com), so i figured it’s the same place. Will try that other forum.

This is the Ubuntu Community Hub, which as stated on the first screen is for “co-ordination of the Ubuntu project … not for technical support” (the last part is bold red). Yes both addresses resolve to the same site.