Thanks for the quick reply Martin. It's difficult to test as it will be fine for weeks and then all of a sudden the fans stop. Thankfully TThrottle saves the machine. I was too lazy/busy to return the ASUS MB so tried uninstalling the ASUS utilities which are useless anyway and disabled MB...
Thanks for the update Martin. Guess I'll have to return this ASUS MB for an MSI. They've been bulletproof on my Ryzen builds. It hard to believe that ASUS would let such a killer bug go unfixed, but to be honest my experience with ASUS in the past has not been positive.
Any information on whether this ASUS "fans stopping" problem has been solved? Would be good to know while I can still return this ASUS MB as it's a fatal bug. In talking to other ASUS MB users it seems that this is a common problem with many if not all ASUS motherboard models. I've never seen...