Hi
If the GPU would have a failure, it would not be working fine without HW errors on another slot (as it do) I think

If you have an old videocard with 2/3 GB mem put that in the PCIe 16 slot and use that for just video output, you have to change
Initial Display Output to PCIe 1 Slot
Internal Graphics to disabled
and see if that works, don't forget to set the order of the mining cards in your mining software without the vga card.