Black screen and lag on twisted treeline

A week before i played 3v3 and my screen turned black for 2 seconds. Now I have this problem every match on 3v3 like 3-5 times. My ping is usually around 50 and fps is around 220. Anyone who know how to fix this? It annoys me a lot and result in a lot of deaths.

ps i only have this black screen problem on 3V3, on 5v5 it works just fine