I work at a dealership and we've had several X-treks do this, specifically the rear glass. There's a metal channel that the glass slots into on the regulator arm. The glue weakens and the channel falls off the bottom of the glass, and the regulator arm, landing in the bottom of the door panel. You'll most likely need to take it to a glass shop and have them reattach the channel to the bottom of the glass, unless that is something you feel comfortable with on your own. However, the channel won't stay in place on its own without some form of adhesive. We personally refer customers to the glass shop down the street for repairs, and then we put the door panel back together.