I have same variant and is in my most under performing rig compared to Sapphire version of RX 570. I downloaded all possible Bios files from anorach tech as modifying it with PBE wouldn't work strangely. Max I have pulled out is a stable 28.1 Mhash rate, with 29.2 and up it would crash after some hours. Try different bioses you can find in Anorach tech website until you get at least 28 Mhash, this card is capable of running stable at this hashrate and if you want to experiment or are not afraid of frequent rig crashes, you can go up to 30 Mhash with this one.
https://ufile.io/h8a9fLink to BIOS1
https://ufile.io/krxkiLink to BIOS2
https://ufile.io/rz4fgLink to BIOS3
https://ufile.io/p72laLink to BIOS4
All bios for HYNIX memory of the GPU-s.