Cerebrus what is your BIOS version on Pro BTC R2.0
I only have setup this for some friends about 50 rigs of such kind. We didn't move the BIOS at all, the motherboard recognized 6 GPU-s directly without problems (RX 570 8 GB). Personally I have MSI,GIGABYTE and BIOSTAR TB250 which also I haven't had the necessity to change BIOS at all. Both motherboards worked greatly without me needing to do anything else except changing PCIEX configuration from AUTO to X1 in MSI and GIGABYTE boards and only activating MINING MODE in BIOSTAR TB250.
I think you should upgrade your BIOS to at least the version of 2016 you told me earlier if you are having problems. If you can log in then do what I have already suggested, DDU uninstall and reinstall drivers. This board which I setup 50 pcs for 2 friends of mine (who rented the space,added security cameras , made it like a real business) always recognized the RX 570 cards and some RX 580 so we finished the job within one week all rigs were ready and are running since April these ones.
Edit: Code 12 not enough resources error you should try changing PCIEX configuration from X16 or AUTO to X1