One thing that would have saved him was someone who'd listened to his first lecture on threaded fasteners and how to fit them, could read the regulations he was given a personal copy of, and passed a practical trade test.
I think that is rather unfair, If there is nothing to say the shackle should not be tightened down then the natural assumption would probably be to tighten it. The problem lies not with the person tightening it, but with the flawed design that allows it to happen in the first place.. I see poorly designed items day in day out and some actually assembled incorrectly by the manufacturers, because the design and the information are not there to prevent it.