Hi, I found this thread just now so I didn't know the problems some people have with the Aorus Master.
I have the mobo since launch and didn't have any post problem at all. My build was just amazing from start. To add something to the table, I always had my mouse and keyboard plugged in the USB 2 ports, Bios versions F4 onwards, and didn't have any problems.
My ram kit is Gskill F4-3600C18D GTZRX (Hynix CJR), running at 3733MTs CL16 - 1866 Mhz IF and UMC.
For those having the D7 debug led code and unable to post until reflash, what are your VDDP and VDDG voltages? DRAM and SoC voltages?
Your problem seems dram related to me, either the ram sticks, or the associated voltages (SoC and/or UMC, dram vtt, etc), which in some time fails training and stuck the uefi code somehow.
I'm speculating here because I didn't have those problems at all, but I faced instability when those voltages are a little off range. Also, try without setting XMP, enter the timings and voltage for your kit manually, and set infinity fabric frequencies accordingly, and set UMCLK=MEMCLK. In later Bios versions, the motherboard set vSoC at 1.2v when XMP was selected, which is too high, try 1.1v by hand instead. DDRVTT can be left at auto, the motherboard sets it right, at half your memory voltage.
Also, I saw some people having trouble with Corsair memory kits on XMP, which are even in the QVL, hence why I reccomend to enter the values by hand. Try to avoid Hynix MFR kits on this board because it seems to not play well with it.
Try a lower frequency for the ram kit XMP rated value, at XMP timings.
I hope you can solve the problem.