[Alpha4.8.1] Fullscreen Graphics get cut-off

[TriMoon]

Describe the bug
When you run a game in fullscreen, the graphics gets cut-off at bottom where the taskbar is normally displayed.
It does not matter if you have the taskbar set to "auto-hide" or not.
See screenshot of "World of Tanks Blitz" and take note of the bottom part.
https://ibb.co/k4VXMCn

To Reproduce
Steps to reproduce the behavior:

1. Manually install Alpha 4.8.1 from iso to harddisk partition, by copying the needed files over.
2. Create a grub entry appropriatly.
3. Start DM and install the above game.
4. Start the game in fullscreen (game won't start when not fullscreen)

Expected behavior
Game should run without graphical glitch like it did with Exo4.7.

Desktop (please complete the following information):

• CPU: Intel i7-5820K
• GPU: Nividia GTX 1080 Ti
• BIOS: uEFi
• TYPE: Desktop
  https://ibb.co/pR6N8yh

Additional context
Im also unable to run any of my other games, which had no problem on Exo4.7...
Plus im unable to bring-up the taskbar or titlebar while game is in fullscreen, which both worked in Exo4.7

Screenshots
See above...

[axonasif]

Sounds like something broke, we will have to investigate further.