X10DRU-i+ - Dual Channel DIMM 2133p reduced to 1866

[Damo]

As far as I can see looking at the manual X10DRU-i+ | Motherboards | Products | Super Micro Computer, Inc.

My 16x16 2133p DDR4 memory should stay at 2133p? It is a v4 CPU

I have tried changing memory speed in BIOS, made no difference.

To confirm I am using the following slots

 

[RolloZ170]

2400 is reduced to 2133, 2133 to 1866 then. (double electrical load)
search for BIOS option Enforce POR and set to disable.