on what are you running ?
If scrypt/scrypt-n I would suspect that it is coming from the low temp target (temp target 75 and powertune 20 is not a good idea, either you increase the temp target, or you decrease the powertune)
I'll try a temp target of 80 and lower powertune to 15. I'm gunna try force constant voltage too. I saw my VDDC in jumping like a rabbit
EDIT: Still going bonkers. Removed powertune entirely too and tried it.