The naive dude took the cable from the customer and ignored rule Nr.1, "never never trust in the ground fumblers". I bet this lesson he will never forget. Pure luck he killed no one.
But interesting to know how Knaus trained his guys. As we all know, the cables have to be marked incl. CE mark and possible load and they should be able to read at least? Or do they use not certified cables? Cables are not too expensive and i would allways prefer my own.