i have like 6 peices of the 270 A and AR asus and they work with up to 8 gpu rx 570 or 580 easy

are you sure you dont have a bad board? they really have problems with 6 plus vega?

I hope not becuase i like these boards since they have their own power switch too and have been for the most part solid.  I only have 3 vega so i cant test it myself

did u update bios to latest?