My stair buffer started acting up a few days ago. As I was buffing stairs, the buffer would shut off for a split second and then come back on. At first I attributed it to a loose plug but after it happened a few more times on different jobs, I knew it was a problem with the unit. Long story short, turns out that one of the wires (the white one) going into the head of the unit was getting pinched and shorting. The pich point was under the black plastic collar that holds the wire in place as it enters the housing. You would never know it by looking at the wire as it looked fine however after cutting back some insulation and wiggling the wires with the buffer running, I eventually got it to arc at the break. I rejoined the wires – problem solved.