Check out my last reply on this thread: https://answers.microsoft.com/en-us/surface/forum/all/surface-dock-w-surface-laptop-3-external-displays/ddd7a9d0-f064-45fd-96ca-2988cef85f31?page=2
I narrowed it down to an overheating video card on my Surface Laptop 3.
I added some easy steps on how to check yours too, but the gist is that you'll not see problems as long as you can hear the cooling fan running at a decent speed when you plug in your external monitor or dock. As soon as it drops to very slow or off, you'll
start seeing issues with external screens and that SurfaceOemPanel error in the logs. It may not be the same problem for everyone, but it doesn't take long to try it out.
As far as helping with a fix or warranty exchange, I wasn't able to get anywhere. I am luckily still within the return period barely, and didn't hear back from my support ticket as promised today, so I got the return process started.
I really like my Surface, so I'll just take the risk and re-purchase another one in a month or two and see how it goes I guess.
Edit: You can also read through my thread at everything I tried and found out if you want. I tried things like safe mode reinstall of drivers, buying multiple docks, buying a Surface USB-C to HDMI adapter, trying older drivers, trying generic drivers,
and more. None of that helped.