I've noticed this on rainy days and when going through the carwash. Basically, water dribbles down the rear window. I'm assuming it's getting between the roof steel and roof cladding (sail top?). Has anyone else seen this? Any workaround? Maybe some caulking? 
This probably contributes to the overall un-sealed property of the rear window that many of us are experiencing.
This probably contributes to the overall un-sealed property of the rear window that many of us are experiencing.