[savage301]

We also had these issues. We think the problem is that a cooling fan is attached to the output shaft inside the motor casing. When you try and lift an arm, even with reduction, you can stall the motor. You still are supplying current and heating the wire coil, but its not being cooled. And here comes that magic smoke. We ended up using the Keyang motors to drive our arm. They work very well, plus they can't be back driven.