The video card behaves as if it is overheating, although the temperature is normal. How to fix?

Question

Video cards

When I start the game, periodically the screen goes black for a couple of seconds. Often. I started SpeedFan, looked at the temperature - about 50. I googled the allowable temperature for my video card - 81. Outside of games, everything is fine. That is, when the video card is loaded, then it starts. After minimizing the game, it may still flicker, when the temperature drops in SpeedFan - it stops. Tell me something.