Symptom: Pitch motor vibrate at a specific position (typically 90° from level) either when using RC comtrol(frame remains level) and when tilting the frame (camera remains level) this ruled out balance issue. If I set it up in different style such as hanging down or sideways. it won't vibrate even if the home position caused vibration in other style. If I left it in that position for longer than fraction of a second, emergency srop will kick in. In worse cases, it sounded like step-motor losing steps . . . .or a fart.