I’m having similar issues with my x670e master and 2 kits of identical ram. I watched a video and they recommended putting one kit in all in A the other all in B. They are 7800 single rank stick of 16gb.
My case I’m aiming for 6000 to 5800 speeds. I think the termination values are what is important not the voltages. I’m just not sure what ones to try.