Ok, to update this: I tried installing MSI Afterburner and undervolting, but that did not resolve the issue either.
I also updated to the latest gameready driver again (531.29), didn´t help either.
Followed some other random advice and:
-Tried changing the PCIE settings in the bios to use gen 3 instead of gen 4
-Tried putting the card into a different slot.
Neither of them help.
I also used furmark again to stresstest the gpu with no errors.
To me it is hard to see how any of this would be hardware related, when it ONLY happens with Unreal engine 5 and direct x12 enabled (from some games forums it seems that directx 12 might also cause similar issues there).
Trying it on two separate workstations with separate PSUs and mainboards and rtx cards and having the same issue also points to that.
It does NOT happen on all scenes, but I have not been able to pin point what makes them different.
And I still find it suspicious that fps drops by exactly half, if you open any editor windows.