Black screen problem every 20 minute or 1 hour only on 1 monitor

Hello i am using 2 monitor one is dell 144h 2k and second samsung 60hz fullHD and yestarday i start to make my own level in game and boom its just show me black screen and cant do nothing,but when i go unreal engine on second samsung monitor working fine.

I have pc or better workstation
i9 7960 16core
128gb ram

Cant see how to resolve this