@G&T
Thank you for asking my opinion, for which I am duly flattered!
However, as I am not in possession of the facts it would be unqualified opinion only and I am not willing to speculate.
I.R.Pirate: "Would a plain, straight forward cargo shift have this effect on an aircraft?"
Yes. I have watched it with my own eyes some years ago in Angola on a C-130A. Not a pleasant experience and my reaction was exactly the same as the driver of the vehicle in the now infamous video. Cold. No emotion of any kind entered my being during the event. I think that bothered me for a long time afterward, more than the event itself. Difficult to describe and totally unbelievable unless you have experienced it yourself.