I would also double check ALL of the electrical connections under the seat. If the seat has ever been out, or worked on, it is possible for the leads to have been misrouted. When that happens as simple adjustment of the seat position can cause a disconnect, or partial disconnect, of the connector ends.
After I replaced the leather and rebuilt the seats on the 560, I was function testing the adjustments. On the driver's seat I placed it to extremes, then went to restore the position. Everything worked except raising the seatback. About 10 minutes of head scratching accompanied by nautical vocabulary was required before I settled down and started at the simple stuff _ the connection. Looking under the seat I found one connector that had been pulled taut and partially disconnected.
Check the connections then the switches before condeming the adjustment motors.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.