Has anyone else noticed erratic behavior with these sensors? They do not engage every time the truck is put in reverse. I've had the dealer look into it and they said it functioned properly. It seems that a sequence of steps needs to be followed for the sensors to turn on, namely step on the brake, move from P to R then manually release the parking brake. It often does no engage going from D to P or if the gas pedal is pressed to disengage the ebrake. I have had not one but two encounters with my brother's mail box because of this, the last of which left a nice dent in my lower tailgate.