I attached 3DR Gimbal + IMX6 only a bigger copter with CubebBack , running AC4.0.5
The gimbal link is on Telem2 using MAVLink1 at 230k
:
It configured rates itself

If I disconnect the serial to the gimbal connection, then the gimbal is nice and still ... when connected, it will do "random" movements
The gimbal link is on Telem2 using MAVLink1 at 230k
:

It configured rates itself

If I disconnect the serial to the gimbal connection, then the gimbal is nice and still ... when connected, it will do "random" movements