Enable failsafe (if remote gain setting is enabled by AUX on a middle position, which is true at startup before we have a valid rc signal e.g. if radio is off, we'd screw up the gains with the fake 1500 input. Powering up the radio could bring the enable out of range before the source channels are valid, essentially making it unnoticeable that the gains were screwed up even when the enable switch was always off.)