I've done some further testing which I should probably have done as soon as I figured out how to recreate the problem.
I managed to recreate the problem with just a single 4GB stick in slot one. After recreating it, I swapped over the stick to the other one and managed to recreate the problem on that one as well.
After that I booted the computer with just a single 4GB stick in slot 3 and manged to recreate the problem with that one as well.
Every time I tested I verified the ram passed (a single pass) with no errors, before a quick shutdown and bootup, followed by a second test with errors after a few seconds
As it would be unlikely for both sticks of RAM to have the same issue I believe this discounts the RAM as being the root cause? Same with the slots on the motherboard.
Does this mean the CPU's memory controller is the most likely suspect? If this is the case it would be somewhat difficult to explain and receive an RMA so would someone be able to confirm this with a better explanation? or offer an alternative?
I'll add as well that following a memory test with errors shown on just a single 4GB stick, Windows had significant trouble booting, flashing a BSOD, offering system repair options, or running for just a few seconds. One time it appeared the computer failed to even POST.
So once this hardware issue comes about it appears to render the RAM close to completely unusable.