Dick -
Your thought is helping me picture what may be going on. What do you think of this idea?
As you suggested, the "white line" in the first picture is where the ceiling wear strip (the wide white surface beside the white line) isn't aligned with the opposing surface. The color of the line is not actually white, but silver, meaning that the ceiling paint is gone and the bare aluminum under it is exposed. If this is correct, the rubbing needs to be stopped before the aluminum wears through.
Cathy, can you tell us whether the color of the "white strip" is actually white, or the silvery color of bare metal?
It looks like the pressure and the rubbing are severe enough that the wear extends onto the strip at the edge of the ceiling.
It also looks like there is some kind of thin black sealant layer (rubber? something fibrous similar to tar paper?) between the edge of the roof and the white aluminum ceiling itself. The pressure and the rubbing have been severe enough to squeeze out the black sealant, which has been shredded by the movement. Destruction of the seal material could lead to water leaks - also a problem if I recall another post.
Cathy, can you tell us more about the black shreddy stuff?
Finally, if my mental picture is valid, shouldn't there be visible marks on the opposing surface, the one that is doing the rubbing?
Cathy, can you tell us if there are any such marks?
I would check all this on my TM, but it is closed up in the garage and not accessible at the moment. But I look forward to your comments. If this idea doesn't make sense, I will delete this post to prevent future confusion.
Bill