What voltage cuttoff are you using? The mm will limit the current to the motor in order to keep the battery voltage above the cutoff, so the low voltage cuttoff a bit lower and do a speed pass. I once did a bench test with my MM and a weak 3s pack and when the cuttoff was set to 9.3 volts, it wouldn't let the pack go below 9.6 volts under a load.
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