Hi
I have a very similar problem.
I bought a G.Skill Trident Neo 2x16G, have the same motherboard, and a 3600X.
One of the two DIMMs works in every memory slot, the other one does not. The two together do not.
When I use the one that works I select XMP, but still the RAM works on 2133.
I tried voltages 1.35V and 1.40V, did not make it a difference.
Did you manage to resolve the issue?
Thanks