If I install the camera into the gimbal without plugging in the video cable and power on the quad, the gimbal works as it should. IE: It self centers, responds to the tilt control slider on the ST10+, etc.
When I try installing the camera into the gimbal with the video cable plugged in, it is REALLY tight and I notice that the gimbal no longer moves freely nor does it respond to the tilt control on the ST10+.
So I am guessing that the video plug is pressing against the gimbal motor/wires and is causing the binding/sticking of the gimbal. So I was hopeful that I could sand off a bit of material from the video plug to allow better clearance of the gimbal motor/wires.