EzTrac665 runs great, but lately a problem pops up sometimes. I start the engine and release the brake. When I pull the steering handles in, the engine dies if I don't quickly push out on the handles. Occasionally, the mower will shut off while I'm mowing - same issue (after setting and releasing the brake several times, the mower runs fine). Believe the problem is something loose on the brakes connected to a safety feature, but don't know where to look. Help please.