Don't think it can be a bad servo or Rx because the 'reversing' is done in the Tx
When you have flaperons set then you need to reverse each channel individually. Reversing on the aileron channel will only reverse the servo that's connected to the aileron channel. If you want to reverse the other servo then you need to reverse the channel that it's connected to.. that would be channel 6 if you have it plugged into Aux 1.
PS.. sorry, i think you might have to look for another cause of your crash