I noticed it on my first trip this past summer, and it never happened again.
My suspicion is that it has more to do with how you let the roof down than how you crank it up. If you let the canvas flop outside the camper and tuck it in you are more likely to push it up out of the track.
In my case, the canvas got flopped outside the camper because I forgot to latch the roof down after an event late in the 2015 season. My mistake was being in a hurry and breaking from my routine. When I stopped at a convenience store a few miles down the road for a drink, I got a surprise. The roof had lifted and the canvas was hanging out 3/4 of the way around like the guts of a stepped-on toad.
I'm sure that's when it happened because I thought something was weird the next couple of times I used it, but couldn't quite put my finger on the problem.