Take everything apart. Looks like the biggest job. Mine move forward, but now I can’t move it back. The other movements work. Thanks a lot. this really helped me.
Sometimes those contacts need a little bit of sanding as they get corroded (or just dull) and that's what stops the seat from moving - (it loses electrical contact) If you've tried everything else and your seat is still not moving, (and even if the contacts don't look corroded) I suggest lightly sanding them till they are shiny again. I've done this on several vehicles where I definitely thought I'd have to replace the control unit and sure enough after sanding the contacts they totally worked.
Worked for my 1999 Eddie Bauer Expedition. Seat wouldn't move back, only forward until I sprayed it. I had just bought some Deoxit last year for a guitar amp that was making noise when turning switches, sliders and it worked wonders on it as well. Managed to break the plastic clips getting them off of the seat though.