Adjusting Closet Door

It's hing from the top. Hard jolts such as rxr tracks too fast and big potholes or some Interstate will make the the nylon roller come out of the track at on end or the other or both. There is a nylon stop opposite the roller, that keeps it from jumping out but sometimes it does anyway. It is held in place with a quarter inch bolt/screw, or ours is. Use a quarter inch socket and loosen it and raise that end of the door back up and the roller in the track. Adjust the stop to keep it in and tighten easy. Too tight and it will break the stop or squeeze it around and it won't work or it might break.
The door should move easily then. Avoid grease of any kind on it. It will gather lint and dirt and gum up the works.