I've been fighting with the controls on my power seats for years. Originally when I got them I could only go back and fourth. New switch assemblies are still available but they cross-reference to a Corvette part and are VERY expensive so instead I dismantled, cleaned and rebuilt the switch assemblies and that got back all the directions of control but some motors were still weak going one direction. Pulled the power seat carriage, cleaned and regreased everything and with the seat removed and the carriage plugged into the harness it still ran like garbage. I'd blame weak motors or springs but for example if you use the rear switch to raise the back of the seat its weak but if you use the joystick which raises both the front and back of the seat its fine, so there's poor connections somewhere.
Now its losing directions again and on one occasion I moved the seat forward while driving and couldn't move it back until I got home and messed with it. Just wiggling the molded connector that mates with the switch assemblies seems to affect things but it feels pretty solidly attached.