8 of us had SX-9's that did the same thing. Just randomly quit running for no apparent reason. If you went over a corner dot, it would stop instantly. One guy sent it back to Horizon and they sent him an SX12. The repair person actually called that guy and told him to tell us to send ours back in too because we all probably got a bad batch. Overly sensitive thermal protection. So I sent 3 of mine (yep, 3. 2 in Carpet Knives and one in my Mini-T) back to Horizon explaining the problem and 2 weeks later I have 3 new SX12's. Email Horizon's service and they'll take care of you.