[suicideneil]

My bad, didnt spot that.

Im not really sure what to say- sounds almost like the esc is 'miss firing' rather than the firmwre being the issue then; could be a few or several bad fets, especially if the esc is getting really hot quickly like that ( and the motor works fine with an MMM, right? ).

I would say it's time to send the esc in and get it looked at / repaired or replaced- form on the support page of the castle website.