Email back from tech support today.

Hello,

From the stats you have submitted below it appears you miner is running at 624GH/s, this is likely to be caused by the odd cores disabling.
We are soon to be releasing the tuning suite for our November miners. This will allow you to control the voltage input of each die individually. Increasing the voltage on the dies with disabling cores can stop these cores from disabling.
The firmware will be released onto our website soon.