Correct. How accessible is the plug on the control panel? Be sure to pick the correct purple wire (I see there are two) I'm worried that you have a permanent short to earth inside the panel or on the wiring between the panel and the ECU. It may override any attempt to return the back of the seat to the upright position. Disconnecting the panel and putting an earth on the green (or purple?) wire will take a faulty control panel out of the "equation".