I know you have to be exactly right with FRUSDR, I was rushing through it with the Phantek build, and it (the case) had a fan header, that I had all the other fans plugged into except for the one of cpu1 - which was the signal for the fan header. I was stupid when filling out FRUSDR, and kept saying that sys 7 fan, and cpu fan 2 were in use (because technically they were plugged in the header) but not the motherboard - just a simple brain fart. but of course you get to the end of frusdr - and it ramps back up to full, because it detects a fan failure on the ports you say should be working. Maybe something like that causing you issues?
I should say, if you do make a f-up in FRUSDR it is easy to go back into it and re-enter the correct info - so not so critical to get right the first time haha, I think I went through it 3 times.
the motherboard serial info missing from bios - couldn't that also be from FRUSDR - as it asks you to fill out that info if I remember correctly - you could probably pop it back in there.