Camera spinning

When I manually set the camera's yew & pitch and so on with this code:

myMotor.SetTargetYawPitch(_yaw, _pitch, 0);
MainCamera.fieldOfView = _fov;
CameraController.TargetFOV = _fov;
CameraController.AnchorOffset = new Vector3(0f, _yOffset, 0f);

Sometimes the camera will just spin out of control when I move the player character. Eventually if I mess around with the mouse and moving around and such the camera will go back to normal but...

Any idea how to stop this from happening?