We are having problems with our GT65 breaking belts. We have taken it three times to the repairman and it broke this time after only two hours of use. Belt looks chewed. My husband has the mower taken apart to check for sharp parts on the spindles but has not found any. Does anyone have an idea as to why these belts are getting chewed. They cost about $60. It is the main belt. Only mowing a yard that is mowed often so high grass is not the problem. Thanks.