I have a theory about your problem. There was a manufacturing issue at the plant in S.C. during the windshield installations on certain recent X5/X6s. BMW issued a TSB to the dealers to remove the defective windshields and windshield seals (from certain VINs) and replace/repair. Yours may have been missed (likely) or was improperly repaired at the dealer (I think this would be unlikely, the training that the BMW Techs received on this repair was quite extensive).