troubleshooting xmp instability

Hi,

I have an asus z170m-plus motherboard (i7 6700k cpu) which all in all has been acting okish, however whenever i turned on XMP in one or two boots i get an overclocking failed message from the bios and have to go back to default values. My memory sticks are GSkill Ripjaws V (4 sticks of 8 GB each) with a rated frequency of 3200MHz and i had the problem with just two sticks occupying the black slots as well as only the grey slots on the mobo, as well as all four.
I've been going over this in multiple forums over the last year and noticed that similar problems occur with other Asus mobos as well. Does anyone have any experience troubleshooting these kind of problems with other Asus Z170 mobos ? I tried increasing the voltage on the memory chips (by 0.01 more volts) but couldn't stabilize it like that either?

Please help.

I didn't find the right solution from the Internet.

References:-
troubleshooting xmp instability - Hardware Canucks
Custom explainer company

Thanks

stress test your GPU.
MEMTEST your RAM at stock settings.
stress test your CPU overclock with the RAM at stock settings. Need to run something that stresses your CPU, RAM, and GPU at the same time. I like running IBT at custom with 95% of my RAM, and Furmark at the same time.