Since I'm new and don't know how to attach a photo, I'll just put a link: https://www.dropbox.com/s/ej3e6ms72sddbu3/20170626_203846.jpg?dl=0

Hardware: iFlight controller + iPower 2804 w/ 5048A Encoder (PWM mode)
Custom G10 frame

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.

Thanks in advance