Initialisation failure only when secured to mount - hikvision ds-2de4a220iw-de

After powering up, as expected the camera pans, then tilts, then moves to home position and sets, activating surveillance mode. As soon as this is done when the camera is on the mount, the camera seems to think the home location is on the opposite side, hits the farthest tip back point and knocks as its trying to turn past the point that it can.

Taking it down and holding the camera off the mount, works fine, soon as its put up it happens again. Any ideas?