replace all of your risers
do you have any missing device drivers in device manager?
ya man, test each card till error appears, replace riser on the faulty one may fix it (hopefully) most risers have a terrible fail rate, sometime right OOB, sometimes after a few weeks.months mining

i run also a free iobit softwear called "driver booster". free and works. it usually finds drivers for "PCI-E" stuff, and have had it help having all those updated
keep in mind you DONT need all the audio drivers for each card installed, as they will just eat up resources
Here's the thing. I plugged GPU 1 and 2 in and it crashes. Then I try GPU 1 by itself and it works. GPU 2 by itself and it works. So it cant be the risers can it? I didn't change the risers, I just unplugged the other ones from the motherboard. Whichever one I leave plugged in will mine just fine.