The roof bow is held on to the glass roof with a lot of very thick urethane. The bead is almost 1" wide, by about 5-6mm tall and runs around the perimeter of the bow. UV exposure would not cause that to lift, but if the urethane is no longer bonded properly to the roof glass panel and it's starting to lift, that's a different type of failure.
We see variances in roof bow alignment and height across all the AIRs we service.