Weird lightning Flickering Issue

On my Computer I run into a weird Issue.
The Brightness seems to change Randomly when i look in specific angles.
I reinstalled the game completely, but nothing changed.
Whe I turn on the flashlight this does not happen. (It seems to have something to do with map-brightness).
Watch the Video if you are not sure what I’m talking about: https://youtu.be/-pU44Ue-1Ok
I’m using an AMD Radeon R9 290
and an AMD FX-8350
running on Windows 8.1

Have you updated your drivers?

Hi I’ve got the same problem but with skybox, if you have Overwolf, try to disable it, or try to disable **HDR
**
Edit : Solved for me it was **Overwolf!•
**
Others topic with this problem too :
http://forum.facepunch.com/showthread.php?t=1506602
http://forum.facepunch.com/showthread.php?t=1507587