Possibly the strangest thing i have ever seen cos i know sometimes in this map i see shadows cover like the majority of the map and then dissapears but as for this you might wanna try reinstalling graphics card drivers or reinstalling ddons for gmos entierly
The possible solution could be to change your "Shadow Detail", this is a common problem.
It was Overwolf for some reason. I disabled it and now everything works fine. Hopefully they'll fix it.
it is overwolf...i have the same in L4D2
it’s the shadows in your head light...