Originally Posted by GT35R

It could just be a high resistance or intermittent OC in one of the motor phases. I thought my sidewinder was stuffed yesterday till I pulled on the motor bullets and one came right off. It would work when I gave it a kick start otherwise it just cogged and didn't move.
If you're swapping ESC's maybe the coincidence is that it made better contact when pushing the connectors together with the MM. I would try another motor going straight into the MMM bullets - just holding it there to make contact if you don't have the right connectors - before assuming the MMM is no good.