Ariens 926003-ST1332LE repeatedly throws the wheel-drive belt off its pulleys. Went through every adjustment possible. Still no good. Belt seems fine. The largest pulley near the friction drive is designed to tilt in and out of alignment while engaging and disengaging the drive-wheel friction disk. This misalignment tends to derail the belt. Inherent machine design problem here? Suggestions or solutions are welcome. Thanks. Carl