Originally Posted by Overdriven

The esc has two options to engage reverse. You can have it set for throttle, brake, go back to neutral, then reverse, or directly from throttle to reverse. This is an esc setting, changing the Rx or Tx wouldn't effect this. It is possible the esc is not calibrated to your new Rx or Tx and that's causing the issue. Anytime you change the Rx or Tx you need to recalibrate the esc to them. Make sure the throttle trim is set to 0 and the EPA's are maxed out in forward and reverse to get a good calibration.