My custom 3 axis gimbal has been a nightmare to tune. I have suffered from this one problem where the roll motor has high pitch oscillations when the pitch angle is tilted down from level as seen in the video. I have tried different IMU locations, motor powers, stiffening the gimbal, and far to many PID combinations to call me a sane human anymore. The only thing that helped was lowering the motor powers drastically, like to 80, but this is a band aid because when I fly with it under my S900 with this setting, it does not have enough torque.

Yes I have done the 6 point cal on the frame and cam IMU. I am not a noob to tuning and this is really leaving me scratching my head.

PS I have tried adjusting my LPF and gyro trust with no change!