Weird M.2 Issue w/Asus P12R-E-10G-2T Xeon MoBo

Having trouble getting PCIe NVMe M.2 SSDs to reliably detect in the M.2_2 socket… they work every time in M.2_1 and in other systems.

I’m trying a Kingston D1000B 960GB and a 500GB WD_Black S770. The S770 will detect on the first boot-up after a CMOS settings clear (via jumper), but never any subsequent boot (which is basically useless, since it dumps you to BIOS Setup and you have to save & reboot after).

Weirdly, I have a Samsung 990 EVO PRO 2TB that detects in both slots just fine, but I was hoping to leave this one in the Gen4 slot (M.2_1). Kingston support has confirmed the D1000B should work fine in the M.2_2 slot, even at PCIe Gen3 x2 speeds (which is what I wanted).

ASUS support has not been very responsive so far, telling me to try typical pedantic things I’ve already done and suggesting that it’s the SSDs and not their motherboard/BIOS. Initially I thought maybe it was just a faulty slot/socket, so I actually purchased a second P12R-E-10G-2T for a second system I am building and it’s happening on that motherboard unit as well, reproducibly.

I’ve even tried three different BIOS versions on both physical motherboards… anyone run into this or have any suggestions? Trying to escalate my case with Asus now after the last support rep gave me a vague suggestion of “try changing PCIe options in BIOS” (regarding what? to what? nothing obviously for the M.2s in there…) I also made a Reddit post that was less than fruitful – so many people ask for Support in that subreddit it’s mostly all just noise.