I have several of these motors. At first I thought there was a problem as my initial experience was the same as several other contributors – eratic behaviour, jaming on the end stops, constant motion/oscilation etc.
However, the problems were only apparent when driven directly from the Arduino UNO board – even with an independent power supply. On the scope the pulses intermittently have the trailing corner cut off, resulting in an inprecise pulse width.
If you drive the servo from a Servo Controller or by powering the motor directly, then it works perfectly.
