I have the same problem, there is such an error on some maps I don't know what it depends on, the gameplay itself is really nice although I played with a friend, he said some errors, e.g. lying characters or characters have their heads turned the other way. I was playing Half-Life 2 Campaign https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=283549412
Gameplay is really good but... bugs and glitches

i think you need to put it mat_fullbright 0 or 1

Ey I know what to do...turn on HDR on the options menu

I did it and it worked