The 780 power seats can be adjusted manually. Your car should have come with a short, semi flexible crank (‘L’ shaped about 10” – 12” long and about the thickness of a metal coat hanger). This can be used to move the seat forward or aft and the seat back up or reclined. To move the seat forward or aft, stick the crank in the hole of the plastic cover located on the outboard side of the seat where the back and bottom meet. Start cranking; be patient – it’s slow moving. To move the back of the seat, you’ll find a cable under the back bottom of the seat.

My 780 seats had the same problem, sometimes the buttons would work and sometimes they wouldn’t. I removed all the inline black boxes located under the seats. For the 780, they’re not really necessary. I think some of the boxes are to prevent the seat from being moved while the back is inclined forward and others make the seat move forward automatically when the back is inclined forward. I just got rid of all that junk and wired the switch outputs straight to the motors.