Our boat is new. It's only a couple of weeks old. Our problem is when we put on the mooring cover and try to zip up over the door it always comes up short to the point that if my wife and I pull with all our might we can get the zipper zipped but it's so strained we are afraid of either ripping at the zipper or having the zipper fail completely. We have put it on 4 times and its always the same. Has anyone else experienced this? Does the cover stretch with time?