You are using DX8. Try to change to film grain mode (old style slender) instead of screen noise (new, better style) so you don't receive any problems.

Its a bug that appears for some clients (your screen is melting if im correct instead of just slightly distorting). Still trying to figure out why it occurs.

Update: try this to see it it helps: http://gtm.steamproxy.vip/workshop/filedetails/discussion/171728689/864977025746553651/

According to most players, a temporary fix is to set Texture Detail to Medium. Worked for me (I had it on Ultra High).
ESC -> Options -> Video -> Advanced -> Texture Detail

Hope it works for you too :D

And I hope this gets fixed at some point, and that it is going to be distortions (Slender: The Arrival style) that higher texture detail allows ;)

Nah, enabling blur seems to fix that, without changing texture quality. Tested on few clients so far.

when i try to play it says im missing a map then i got the map but it still said i was missing it