It's a simple fix really once you see the problem. At the outer, rear, lower base of seat back exists a microswitch with a spring and lever above that. Chances are good that the spring came off and that the metal lever is loose (moving freely). If you can find the spring, re-install one end in the lever (small hole for it by the bottom) and use a plastic tie-strip to attach the other end of the spring to something solid, forward of the microswitch. Doing that will hold tension of that lever against the miscroswitch and the seat will then work normally.