When I spawn Left 4 Dead models (before&after patch 81) the world sometimes glitches out

When I spawn Left 4 Dead models, the map and models all start to flicker, parts dissapear, the map flickers, colors don’t look right and textures get fucked up. This happens with NO other models so it’s not my graphics card, I just want to know why it happens.

Save me, FP.

anybody?