We've now found two screws on the floor down in the pocket area. We think these two screws were used to hold the channel to the ceiling. When the door is fully in the wall/the pocket area and we just begin to close it, the bottom of the door moves first. This is because the full weight of the door is hanging from the channel under the part of the channel where the screws fell out. So not much is holding the door up at that point. So the solution seems to be to remove the door and replace the screws that held the channel to the ceiling. The problem is that I don't think I can get my hand and arm into the pocket opening far enough to replace those screws. Do you all have some good ideas here?