I have 8 of these boards. I noticed something that maybe will help you. Sometimes when I restart the system it starts with less than maximum nr of video cards and is random, 5 cards, 7 cards. in order to bring them all online i have to take out the battery from the bios, then put it back in and afterwards it starts with 13 cards everytime.
Does it matter which pci-e slots are used when you have less then 12 GPU? I have already isolated almost everything except the way the risers connected to the board and the miner itself.
I connected 6 cards to the black pci-e slots first and the other 2 to the first white slots.