[What's_nitro?]

It could be the same "problem" people are seeing when the go from the MM to the MMM. Some were complaining that a setup which ran fine on the MM was now getting too hot with the MMM. The FETs in the MM may be much lower resistance than your 60A controller and so allow a much higher pulse current to pass through to the motor. Is the motor getting hot too? If not, I'm kinda stumped... That's all I can come up with right now.