I just got my 15 R4 in the mail yesterday, and I had an extra m.2 2280 drive to use along with the included 256GB one. I plugged it into the other open slot, and it is not recognized in disk manager or BIOS. I switched the slots of the two drives, and then the WD one that I had was recognized, and not the included one. So I have a feeling it has something to do with that slot. I also noted that RAID was turned on instead of AHCI, if that has anything to do with it. Any ideas?