I might murder my rig...
my whole system freezes up and I have to hard reset. When isolating the GPUs this still occurs. Does not matter if I have one running or all 6.
Have you tried using one GPU directly plugged PCI-e x16 slot on the board, then fire up miner?
I suspect that is it my motherboard or power supply.
If the above setup runs successfully, you either have a bad riser or power supply issue