Thanks for all the time you spent investigating this! ? It would be funny to submit a bug report with AMD just to see their reaction.
Are you using Win 7 64-bit SP1, AMD SDK 2.91 and GPUpi 3.2 non-legacy with HPET off?
Only letting this one go because my board refuses to post Sky-X chips now Fine with Kaby-X for some reason.
You can find all my subs with this chip here, this was from my first ever cold session on Sky-X and also my first session on CBed chip so there is for sure some room to squeeze out more MHz.
400 euro + shipping from Australia