Memory Loss after BIOS flash to 2.0?

Hi, new here, and I'm not sure EXACTLY when this happened, but starting from the BIOS the mobo shipped with (1.5), my X399 Taichi and TR 1950X at some point went from having almost the entire 64GB available to Windows & Linux to suddenly having only 47.9GB "usable" in both Windows 10 and Ubuntu live. If I had to guess, either the 2.0 BIOS I flashed to yesterday or a cpu microcode update caused this sudden loss of available memory. I tried downgrading to 1.5 or 1.8 BIOS (what I've been using for weeks before 2.0 came out), but either the microcode doesnt downgrade, or the BIOS was never the issue.

Its worth noting that the BIOS shows Quad-channel enabled and full 64GB. Even windows says 64.0GB installed, but only 47.9 usable.

Things I've tried:

1. Loading UEFI defaults in the BIOS
2. Disable/Enable XMP
3. Bumping SoC Voltage to 1.1 from 0.9 default.
4. Bumping LLC to Level 1
5. Loading the latest Ubuntu (17.10) from a live USB stick, still only 47GB available.
6. Swapping the sticks from the recommended (2) slots to the (1) slots for troubleshooting.
7. Running a memory test with windows 10 memory checker, no errors.
8. Downgrading to both 1.5 and 1.8 bioses, no change---not sure if this goes to an earlier version of cpu microcode or not.
9. Taking the 4 Corsair Dominator sticks from my other box and swapping them in, same result
10. Changing from NUMA to UMA mode, no change.

Like I said, at some point after flashing from 1.5 to 1.8 (the day I set it up, weeks ago) the RAM was working the way it was supposed to in Windows, with nearly the entire 64GB available (63.9 or something like that), but I just noticed after flashing to 2.0 yesterday and running benches that only 47.9 was available.

The Kingston Ram I use for this box is on the approved list, 4 sticks: HX426C16FBK2/32

The Corsair Ram I troubleshooted with is CMK64GX4M4A2666C16, 4 sticks.

Anybody have any ideas?

Yeah, I tried all that---including trying 4 completely different sticks of DDR4 from another box and the A1, B1, etc versus the 2s. I just think its weird that the 2.0 BIOS flash yesterday was the first time I noticed the RAM "available" level drop---plus, wouldnt the RAM not show up in the BIOS at all if they werent seated properly? The BIOS shows all 4 sticks, 16384, and Quadruple Channels.

I was hoping it was just a bug with the latest CPU microcode, but I'm starting to think maybe its a bad memory channel; the problem is obviously not with the RAM itself, as the exact same issue shows up with the memory from my other box, which is an Intel setup with Corsair memory with the full 64GB available. But, put that very same memory in my X399/AMD system, and the 47.9 shows up.

Yeah, I saw that post (and others) earlier, the only thing I havent tried that they did was re-seat the CPU (suggested in another thread and actually solved his problem) , which I guess I will try later today when I get home from work, but I am not optimistic that is going to solve anything---after all, the memory *did* work just fine at some point, and I havent done anything to the water cooler mount to make me think the cpu somehow shifted.

Nor have I---but it appears perfectly in the BIOS, and technically Windows detects that 64GB is installed, but for some reason, only 47.9GB is usable. I'd say it was a Windows issue except the exact same thing occurs booting into Ubuntu 17.10 via the live stick.

I've tested the A1,B1, etc. slots, and the A2, B2 slots with all 4 sticks, and the same thing happens. Its almost like theres *some* option turned on the BIOS for an onboard peripheral thats causing ~16GB worth of memory addresses to be taken up for no reason, but I'll be darned if I can figure out which one that is. I've already tried moving my video card (Vega 64 w/c) from the 2nd slot to the 1st slot, no changes. Gonna have to try reseating the cpu tonight, but again, I dont expect that to change anything.

I feel like such an idiot....the bottom two screws on the cpu loader mechanism were either never tightened, or somehow came loose. As soon as I tightened them up, the problem was fixed.