7 years ago
The track may be broken or even simply dirty.
Your plastic wheely things could be cracked or have a flat slip over. They replace easy.. Then adjust the spring tension. Assuming the actual floor rails are not flattened or cut for de-rail.
The door should have adjustment points on the top and bottom to tighten the wheels against the tracks. Check the top and bottom of the outside edges of the door for a hole with a screw adjustment inside.