Got passthrough working on x570, 5600x with a gtx 660 and a patched bios for uefi from evga. I ran a game and it worked fine, tried with a newer one and got to the menu and the screen went black, rebooted the vm and the card suddenly has code 43 again 
Dmesg had vfio-pci 0000:2d:00.0: vfio_bar_restore: reset recovery - restoring BARs a few times
Now I always have code 43. A Ubuntu guest works fine with the card too.
Is this a reset problem or some weird driver thing on Windows?