Hi there, I was having the same issue. Asus Z170 Pro Gaming with CMK16GX4M2B3200C16R (Vengeanze 3200 Mhz)
I was having random boot problems during POST when enabling 2800/3000/3200 MHz, no matter the voltages or timings used.
I asked for a replacement to Amazon and they sent me a new pair of 8 GB modules. I noticed that the revision was new, 5.xx and the previous ones were 4.xx.
The thing is that I activated XMP and instead of having a TRFC value of 420 clocks, I have a 560...It seems that this parameter affects stability with little impact on performance as I read somewhere.
Since 5 days the problem seems to be solved. Maybe you can try to set this parameter at 560, or look what value CPU-Z reports for you.
Hope it keeps stable!!
PD: BTW i tried before the turbo mode on fans but that didnt solve the problem...
