the problem with the monitor and games

Hi all, recently I bought a monitor asus rog pg258q. the monitor is great, but noticed one oddity. In some games everything is fine. And some and it seems like it was that first time it saposcol, it switches to the menu of the game and the monitor starts at 5 seconds off, then again turns on for a second and goes out again. and so the story continues. then like in the settings change the resolution to FullHD and stops. From what such hogwash can be? Connected via display port. But sometimes the problem begins in the game, which I played without any problems. Where to look ?