i had the same problem. but its not the encoder. the joystick is getting stuck on the bottom panel. when your controller is stuck right, be very quiet and slowly move it left, you will here a click and then it stops. the problem is that the controller sits to close to the bottom. you could just remove the bottom panel, or sand it down.
but my solution was: i bought a slikstik quad and couldnt be happier.
frank