CPU Fan Header fan stops spinning

[OB1]

Motherboard X570 AORUS XTREME (rev. 1.1)

I notice sometimes when I boot my pc or when I amend bios settings sometimes and not all the time but it is intermittent sometimes the CPU fan will sometimes spin up and sometimes it will try to spin but it just does not quite spin up the fan will rock back and forth it is if power is not getting to the CPU Fan header I have swapped the CPU fan to the optional fan CPU fan header and still the intermittent fan will try to spin I am using the NH-U12A with Dual NF-A12 120mm fans, so I am using both the CPU FAN & the opt CPU Fan header in essence I am using both CPU fan headers. The fans are 100% working with no faults and are only 13 months old they have worked without fault up to installing into this motherboard and today there is nothing wrong with them I have even swapped with another 120mm fan and it does the same thing so considering the CPU fan header sometimes spins my CPU fan and sometimes it does not I would like to ask your opinion do I have a faulty motherboard as I have never come across this issue in all the 30 years, I have owned a custom and built my own PC builds. The motherboard is only 3 weeks old and has been in use for the last 2 weeks now. This by the way is the only issue I am having with this motherboard the fans do spin up and have been doing so on a regular basis but it is just if I go into bios to say change boot configuration or set the XMP profile or the F-Clock Fabric anything really sometimes the CPU fan wont spin the optional fan spins but the CPU fan stays static I swapped the fans round and still the cpu fan will spin and sometimes it will not, I hasten to add if I just shut down windows and restart then it works but only sometimes when going into the bios the fan stops spinning and sometimes also coming out of the bios I would assume with no CPU fans spinning the CPU would get that hot the computer would eventually shut down so the only way to remedy it is to hold the power button on the front of the pc case and restart the PC then the CPU fans spin up as normal it is an intermittent fault that I am experiencing so what do you advise. I don't know what else to do really. The other fans in my pc case are unaffected it only relates to the CPU fan headers only, nothing else.  I contacted Gigabyte customer support and they say keep updating to the new bios which I have done and yesterday I had multiple times when the CPU fan will just stop spinning remember to rule out the fan itself I swapped it with a spare fan and it does the same stops spinning so I know it is not a fan problem what do you all think should I RMA the motherboard what is your though on this or is it maybe a conflict between the SIV fan software and the bios are they in conflict with one another and have you any suggestions I can try. Apart from an RMA I do not know what else to do as I will be without my PC for weeks and maybe Gigabyte will just return my motherboard without finding any issue, so I am looking some advice. Thank you.

[shadowsports]

Greetings,
Only thing that comes to mind are fan curve or power management profiles.  These can be set in BIOS or in software as part of Gigabyte Utilities.

I would first confirm no profiles or custom curves were set.  Your CPU fan should never stop spinning (ever). 

If the behavior occurs with different fans, its not the fan itself
If you use default settings for Fan behavior in BIOS and do not have any custom Fan Profiles running of set in SIV, I would return the board to the place of purchase for exchange.  If that is not an option, then RMA. 

The BIOS you decide to run should in part be determined by the CPU you are using.  Latest is not always best.  Nor should it be a solution for to a CPU fan that stops spinning after making a BIOS change, unless (the BIOS) its known to be faulty.  I doubt this is the case and if it has occurred with 2 or more fans with 2 or more BIOS revisions, then something isn't right with your BIOS settings, fan curve or the board itself.