Turned out to be the ram sticks.
Faulty memory is my bet
I'm having a Sheldon Cooper moment just about now.
Any change that you have to make manually will be wiped out when you have to do a BIOS reset. Just exchange your sticks for a pair that works correctly even at default settings (1.5v) and if required clock up from there.
I have run 880G boards that will easily get a 1333 stick to 1600 speeds with no voltage increase. Sticks used were G.Skill value RAM - the generic green PCBs.