Anyone encountered this film on the windshield and found an effective way to remove it? A week ago, we placed vinyl letterings across the top of the windshield for a customer. Now some of the letters have come off and few others are beginning to lift. I'm suspecting this windshield was treated with Rain-X at one time. Since the customer bought the truck used, he can't provide any history on it. Our cleaning and prepping the surface have always produced positive results. All the small letters we put on the rear side windows are holding up great, so Rain-X is my primary suspect.