Panoramic sun shade detached from rails and recoiled into the assembly while driving on the highway. The shade was in a static position when it happened- it was not being retracted at the time. Available for inspection, but has already been repaired by dealer. A very loud cracking noise was heard when it happened, which startled me and could have caused an accident. It is a relatively new car and had been retracted probably a total of 20 times. There was no warning, and the entire headliner, pillars, and glass had to be removed to repair. It is apparently a common occurrence due to cheap plastic clips that are used.