Have you contacted Sapphire support, they may offer a new Vbios if it is unstable clock issue.
I have tried to communicate with amd and sapphire, I have sent reports and e-mails. I have searched for other bios but I have seen that it is very risky.
I've been with this problem since 2015 and I do not see any news that this is going to change.
After almost two days testing, has continued the same, black screen has returned.
I have tried several configurations with msi afterburner along with clockbloker, afterburner only, clockbloker alone, and nothing solves it.
the only thing I can do is wait for my nvidia 1070 to arrive.