I have a Garmin sat nav with a suction windscreen mount. I have had the sat nav for about a year and in the last couple of weeks the suction does not appear to be working correctly. Simply stated I attach the suction cup against window as per normal and it grips (as per normal) but when I come back to the car in a couple of hours, or the next day it has fallen off. It appears to grip well when put on first. This has only started happening recently. Has anyone else experienced this and if so is there any way to rectify it and restore its original grip?