Need to apply basic trouble shooting with your rigs, Take one rig getting that GPU FAULT error (Assuming HiveOS or LINUX?) and test the basics, Integrated Graphics, RAM/MOBO etc no GPUs and if it boots, then move on Add 1 GPU see if you get the error and so on. IMHO it seems like you may be having Risers Issues/faults.
I think it is totally riser fault. I had one rig of some of my colleagues which I am managing and after checking the risers, 007c was the versions they were using, I saw strange behaviour, some of the GPU-s couldn't mine, Nicehash ended always with a terminated and not being able to benchmark.
At first I thought a bad bios, or a card fault but after testing everything , decided to try changing the risers to the latest version and after that, everything went back to normal.