PC Graphic problem, big black stipes at start, unable to play if I have 2 screens active

Hi,

I have a graphic issue which does not let me play FH4 on PC if I have enabled 2 screens.
Both are WQHDs, and the game starts at full screen mode on my main one only (that’s fine!), while the second is untouched, but just after the start at the intro screen there’re graphic glitches (big black stripes jumping I’d say) and I cannot proceed further.

If only I set the W10 graphic setting to only 1 screen and restart the game - everything works.

specs:
2x ASUS PG279Q
i7 6700K, 16GB RAM
MSI GTX 1070, nVidia 399.24 driver