The photos of the arm joint that separated appear as rusty as an old car frame. This makes me wonder if, due to the rotational component of the car cluster; any moisture in the arm will be flung out during operation and concentrate at the end where it broke (centrifugal force). The fact that there are wires passing through the arm means there are openings at the other end which could allow water entry. Was the interior of the arm structure coated with any kind of oxidation inhibitor, weep holes? Just musing.
