CorneliousJD

I had the same thing in Call of Duty Cold War, so instead of disabling DOCP enitrely though I just lowered it to 3133MHz and it's been fine and happily stable since then. Slightly lower timings for staiblity ended up being the solution for me.

Also I don't appreciate the condesending nature of your comments. 
 
I am trying to educate myself beyond just this "3133 = good" "3200 = bad" 

Technically XMP is deemed an overclock and the fact that the RAM is tested as successfully running at those speeds it ultimately depends on the motherboard and the memory controller of your processor. 
 
Also, I see from your parts list that you are running 4x16GB memory sticks thus populating all DIMM slots. This is possibly the worst type of configuration when going for high frequency and tight timings (high-density RAM modules and having all slots populated). 
 
What you can do in order to get the speed back to 3200MHz is to loosen the timings or bumping the voltage to 1.4V or 1.45V, possibly even both. Still, keep in mind that if you loosen the timings too much, it would be better to run the RAM at 3133MHz with the current timing config. 

Yes there is. You can do a couple of runs of memtest. Or, something which I personally do when I want to test RAM after overclocking to use the built in stress test in Aida64. I like it because it is quite versatile allowing you the option to stress test only the memory. Usually after running it for about 3-4h you should have a pretty decent indication if it will be stable or not. Alternatively, Intel Burn Test is also good in catching memory errors fast. 

Excellent, thanks for all the options. I'll work on this tonight