I bought a Polaris 9300xi in July 2011 to clean my 16x32 vinyl-lined pool. I've used the cleaner every 2-3 days since then and it does a great job cleaning the pool. Near the end of August one of the wheels broke off where it attaches to the hub leaving about a 1 inch hole in the center of the wheel. I called Polaris and had to drop it off for repair at a service center about 45 min away. They had it for about 2 weeks. I used it for a few weeks after I got it back and this evening another wheel broke off (same thing - about a 1 inch hole lefy in the center of the wheel). I called Polaris and they are sending me another wheel which I will have to take to the service center for repair (they said if I repair it the warranty will be void). The representative said they have had this problem with some of the units. Has anyone else experienced this and has it happened more than once?