I had the same issue when I picked up the vette. Got the car home and moved the passenger seat forward. It wouldn't go back, so the wife had to wait two weeks to ride in the car.
The dealer ordered the replacement proximity sensor that is behind the carpet on the wall behind the seat.
Sorry to hear that your passenger power seat will intermittently not move backward. I understand the displeasure when dealing with a matter like this. Although you're seeking opinions from others, you are more than welcome to keep us posted on what you hear after calling the dealer. If necessary, I can also communicate your concerns with the Customer Experience Managers (CEM). Please know that you're welcome to message us privately if you would like to discuss this further, or if you simply want this matter documented.