Hi Jon,
I am wondering how your controller Hall sensor (powered by the pump/controller battery) can be affected by the pull down of several servos on the Rx battery? The only connection between these two systems should be a one way from the Rx to the controller via the throttle 'servo' feed from the Rx. I am probably not familiar with your systems but possibly you have had some misguided information? The effect caused by the pull down of the Rx battery voltage should be somewhere in the neighbourhood of a PCM failsafe condition, but should not affect the Hall sensor, unless your are somehow using the same battery for both systems.

Sorry to sound so upity...
Len Gladstone