This was my problem I flashed the bios F10d from here on my Gigabyte Aorus Master and well all fine, Then a newer bios is now out f10 from giga.
So went to flash using QFlash and got OEM ID Missmatch. so then i try'ed EFIflash and still got the same error was like WTF.

Well to get round this I used the MB switches and switch to the backup bios that I had never used so was still on F4, Then i used the EFIflash with the command /DB that would flash both bios's this worked for me.
I'm not sure if many other's have come in to this problem but think I link a way around it unless you flashed a modded bios to the back up bios also then i believe your need a modded EFIflash.exe

Anymore info welcome