If it is like the Airstream pocket doors, it is hung by two bolts with sliders and nuts from the top inside the track. Sometimes the nuts back off. If you push the door up from the bottom and then stick your finger down in the track you may be able to feel if the nut is still on the hanging bolt. It is impossible to see. If it is, tighten it. I have not put Locktite on mine. I just tighten it once in a while. If the nut is missing, it still may be laying in the track. If not, you have to quess what the size might be and with some gum on a stick put it back on the bolt and finger tighten it.