I am having the same issue and tried changing some things in the bio like dmi link speed to gen 1. When I run 4-5 gpu's 1 or 2 of the gpu's drop out. I am also using a corsair hx1200 with rx480 gpu's. I actually have 6 gpu's but one of my risers are out so now I am awaiting better risers and new evga p2 1600w power supply.

I am using a z170a sli plus mobo running 6 xfx rx480's and either one or two of the gpus will stop mining. This also happens when I have 4 plugged in. Also, I am using a Corsair hx1200 psu. Do you happen to have the bios settings that worked for you? I couldn't use your links since they are broken