The resistor itself doesn't cause the problem, it's the limited current being drawn while arming (beeping the motor). When the resistor is hooked up, the MMM attempts to arm, but when it does so, it tries to pull more current. When the current increases, the voltage drop across the spark resistor increases which reduces the voltage at the ESC.
Somehow, the MMM doesn't like the fluctuating voltage.

However, Patrick's warning was given when there was trouble with the BEC in V1. I wonder if it was just a coincidence, or if it would be ok now that the BEC issue is resolved?

so why cant you use the resistor to charge, then arm the esc?:neutral:

That might be a possibility, but you'd have to remember to have the switch shut off EVERY time.

Very true..... my MMM needs to get here faster.