Yeah tried that as well. Tried now to switch motherboard with my desktop computers motherboard and its the same thing.
Tried to flash all 3 cards again with the Vega 64 bios, but still same.
2 cards going at 1750H/s, 3rd at 1100-1300H/s and during refresh the last card drops to 0 then back to same range.
Then after a while miner stops hashing all together.

Very strange..