Each slide rack should have a 1 inch square steel driveshaft going from each end of the motor to that gear pack. Just 1 1/4 inch bolt holds the shaft to the end drive on each end. Go to the end that has slipped and remove that bolt. Then take a post it note and adhere to the outside flange. A note on each end. Measure the end of the slide you did NOT remove the bolt from. Write that measurement down on the post it note. Go to the released side and take the same type measurement. It WILL be different. Push or pull this released slide to match the measurement from the other side. Then go back to where you pulled the bolt and use a crescent wrench to turn the square drive shaft just enough to align the 1/4 inch holes and reinstall the removed bolt and nut. run the room in and out a few inches and remeasure. The measurement should be within 1/4 inch or exact. IF NOT, the redo this procedure. Doug