I've completely solved the issue with a combination of:
1. put water pump on cpu_opt
2. disabled fast/ultra fast boot in the BIOS
3. set cpu_opt to 100% all the time
System is working beautifully at this point. I'm extremely happy with this board now.
My only gripe now is SIV needs to be started once after boot to load the fan profile, and I cannot seem to control fan profiles from the BIOS. I've made the suggestion to Gigabyte to load SIV as a service that runs at startup and loads system fan profiles.
This is a useless forum man, you ask and you answer to yourself. I don't know why this forums exists.
I have a similar problem on a brand new Z170-UD5 MTB. For me is System Fan 1 that does not start.
I'm not sure if it is after the wake up from sleep, or even after a shutdown, but sometimes it just happens. I have set myself and alarm to let me know when it happens, because my system is so silent and I cannot hear the fans.
This is ridiculous, I plan to send the MTB back and buy an Asus.
I'm glad you fixed your problem. You don't know which of the 3 actions solved the problem?