I think that I found the solution.
1: Reinstall the actual graphics driver (I reinstalled the studui version 566.14.
Tell the Installation the rest the driver to standart settings <— very important, otherwise it will not work.
I had the problem in all version of UE and in UEFN. Now UE and UEFN seem to work fine again.
I hope this will work for you also.
best
Jens / CTO at AlphaFlare