iMac crashes

Hi, I have an iMac (Retina 5K, 27-inch, 2020) with to additional HD screens. (which this iMac should easily be able to handle according to the apple site) Unfortunately it crashes often. The additional screens turn green and the main iMac screen turn black. This happens mostly when I have mutiple apps openend. These are not crazy big programs. Just spotify, photo's and some taps on Chrome. But sometimes it also happens when i'm only using something like Microsoft Word.

I went to an apple autorized repair shop, but when I brought it. the problem of course didn't show. I explained it to them and they think it has something to do with a defect in my video card.

I already tried disconnecting one screen. The problem happens les often and without any additional screen it even happens lesser times. But it still happens from time to time.

Is there anyone else who has this problem or knows what the problem is? I already got this problem since I bought this iMac new. But it didnt happen that much and now its getting worse and worse.

The iMac has a:

3,8 GHz 8-Core intel Core i7

16 GB 2667 MHz DDR4

AMD Radeon Pro 5500 XT 8GB

Hope you can help me out!

Thanks.

Justin