I'd try adjusting your voltages first, you could try 1.35v CHA/CHB and eventual CHA/CHB as for system agent around 1.2v did the trick on the 2 5930k's I tried but results will vary chip to chip, and possibly a tad of Vcore while you see whats what.
If your still don't get anywhere then I'd probably look first at swapping out your memory kit.
I like you and others have had funky slot detection problems with this board, mine resolved itself though I probably had changed bios too at that point, I can't remember now, though I'd completely clear your bios too and try again.
But like you I had many many problems with this board, most related to problems getting my Memory kit working stable seems to be a common thread with this board, along with other related memory kit problems.
But I'd start with your memory kit first and and tweaking if required and make sure you test your ram properly as you go.
There's a 3000Mhz guide on here which you may find useful and explains the various voltage settings in this bios , it will give you the idea of what you need to do regardless of ram speed to get your kit stable, without me having to type a wall of text on Xmas eve. lol
Failing that if your still getting no joy and RMA'ing the Kit and the board is a option at no expsense for you then that might not be a bad idea though personally I think you should look at replacing the memory kit first, and trying again.
If you do swap your kit however try swap it for a QVL listed one out of the manual by part code.
As far as reflashing your bios, you can use the Bios flashback feature as outlined in your manual on a usb in the dedicated slot on the IO panel, its a new feature for me on this board so I'm not the best one to tell you about it, as its not something I've had cause to use personally.
Hope you have good luck and let us know how your doing.
