Pat, I had the headlining out, lot of work, but was really banging my head on this one. I found taking the nut and attached washer from the track at the back and above the rear seat (above middle of door) on each side allowed me to slip a piece of timber under the track and get a good view of the channel. (the bolt is captive in the track and has some rubber seating).
I had one track completely off but could not see how to remove the plastic ends, the 2" square rubber part at the rear just pulled down and off. A pin hole and some cracking could be seen on the drivers side channel, just a bit of cracking other side, I was getting water from both sides, drivers side worse. We could spray water into pin hole and see immediately water inside, some running along folds and layers of the steel bracing. Pin hole was/is on the joint where one sheet folds over and joins another.
I smeared more silicone sealer over the area yesterday and will be out with the hose pipe later today (April 1st), will add to this thread the final result.