My sliding door has been getting noisy recently, finally got around to having a good look. it was a real scraping noise just as the door closes. I have the factory swing out step for the door, and the hook that pulls the step out is close to the body, so I thought that was rubbing. That was not it. So I started to look at the rollers etc as it has been a couple of years since I cleaned that all up and re-greased them etc. That did not help either!
What is was, just as the door closes, the track pulls the front of the door in. However the bottom front roller (that supports the front of the door) wants to go straight forward, but is dragged sideways. This sliding across the track is what the scraping noise was. I have cleaned and re-painted where it runs for now, but the rubbing will soon take the paint off again. Not keen on grease in there as that just collects dust. I might try a graphite powder or something in there.
Anyway, it was an interesting find!!
Richard