I got  the same card and did the one click Bios Editor. When i checked all the Straps were changed as per 480 from 1650 downwards. I do get 30.5MH's but my other cards MSI RX580 are stable ...this card jumps  from 30.5  down to 26 then up to 28 then 30 and back to 24 ...Anything i shud try to get it running stable @ 30MHs please.