Pocket door

Just replacing the screws will not be a good fix unless you hit a ceiling truss. If you just run screws into the ceiling then they'll just pull out again. The ceiling material is thin and won't hold weight. Most likely you have wooden truss in the ceiling. Could be aluminum. Doesn't matter. First find where the truss crosses the ceiling. That is where you want to run the screw.
Get yourself a flexible drill extension. I don't know how much reach you need but the extensions come in various lengths so get the length you need to reach where the truss is. You may have to first drill a smaller pilot hole to start the screw. You can use the extension to drill the pilot hole then run in a screw.
It's not a major job but can be aggravating.

Door removal is NOT REQUIRED. You need access on one side or the other to add bigger screws.

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?

YES, the track can come loose as the JACK AZZES will use driller screws to attach the track to the header.

Seems to me we had this same problem and removed the door to support the track in the closed part of the pocket. We drilled a couple of holes in the track as far back as can be reached and added screws.
The door hanging by a few screws is under stress due to the bouncing of the rv on the bad roads so this is a rather common problem.

Your hanging bracket has come loose/unattached. Hope you have an access on one side or another to re attach/connect.

I was a Master at properly hanging pocket doors after having a couple failures in Commercial applications.

I have a love hate relationship with pocket doors!

The pocket door in my trailer is suspended from 2 trucks by a catch on each truck that is attached by screws to the top of the door.

The door can be released from the trucks by moving the catch horizontally allowing the door to drop. I suspect a screw has fallen out from the "back" truck.

The door should be supported by a roller on the floor at the edge of the opening.

It is levelling out on that roller as you close it, but the top is detached on one side.

Release the other catch from its truck and remove the door from the opening and inspect.

At least two pinched fingers must occur getting a RV pocket door out of the opening.

Example of pocket door hardware.