I have no experience with total removal and repair, from what I understand it gets warped and the only real repair is replacement with new, since it involves pretty much tearing apart the entire inside I don't know if I would bother. I have been fortunate that none of my saabs have had this problem. There is a screw fix that some people have tried. I'd start by trying to lube it and work it back and forth with the screwdriver to see if it helps. Also it might not be the distribution box at all, maybe the stepping motor is bad, try adjusting the direction of the air with the motor removed (but still plugged in) and see if the motor moves.