That Happened to my 17 Screw. I didn't use the sunroof all winter and spring. When time comes to use it, it did the same as yours, then it would get stuck open halfway. Took it to the dealer and lucky for me it was under the factory warranty for another month. The service writer told my it would have cost me around $2k to fix it. They need to remove the whole headliner and replace the whole track system. When I got it back I started to use the lube around the sunroof seals so the rubber won't get glue to the other glass from the heat and dirts that falls onto it. It'll happen to all the other vehicle with the all glass roof sooner or later. you just have to keep that sunroof seal ( rubber ) lubricated.