Possible screen, card, or windows problem, partially black patches occasionally appear on screen

Hello!
So, i have a problem which appears occasionally, and for a short time. Part of the screen, sometimes small, sometimes, like a third of the screen, goes dark.
Typically, when scrolling in Facebook, or Google search ...
The patches are square with typically one side uneven, like in the attachment file that I tried to draw...

I am using Windows 11, updated to the latest everything, and 1070 gtx card, also updated (I updated drivers when this started happening, maybe 2 months ago, and updating didn't help at all)
Mostly, I use Edge, so I don't really know if this happens in Chrome too (I can't really recreate it, it suddenly appears and may occasionally appear in the next hour - or so, and then not appear for a day or more)
Also, I can't do a screenshot, because even if the patch stays for longer than a split-second - and sometimes it stays for a few seconds, once I press the screenshot button, it goes away.
Well, it usually goes away if I do anything, like the slightest move with a mouse may make it disappear.

This happens on the Dell U2723QE 4K monitor, scaled to 125% (couldn't read the menus without scaling)

This doesn't hurt my work and is not too bothersome, but it started to bug me really hard. It brings on my OCD I didn't know I had :)

If anyone has any info or knowledge, please help!?