I once had a fully strapped load of chipboard leaning against the curtains on a particularly rough crossing from one night from Zeeby to Teesport…..(flat bottomed boat not for the faint hearted.) but never seen anything as bad as that.
When I was in traffic at Northwest Freighters, late 80s, we had three unaccompanied fridge trailers loaded with Kraft Philadelphia completely on their sides on a sailing from Hamburg to Harwich, I think it would have been the MV Surrey. That was by far the worst, but damage from them leaning against each other did happen on other occasions.