Maybe, I have a heretic thought:
Were the growing container piles above deck, and even above the ship’s guides, not considering the larger transversal accelerations on the top containers?
Would it not be better to stack the containers transversally on the ship, with more flat lashing angles? Indeed, all gantry cranes, all dockside dispositions and all older or new ships were built for longitudinal transport…
The very steep lashing angles of the longitudinally stocked containers, give a very high vertical compression on the edges of lower containers. The pictures show nearly always the crushing of the lower containers.
The ship’s guides help retain the stack vertically, but cannot interdict the millimeter range movements of the containers, transferring the huge vertical forces downwards. Stiffening the lashings could even augment the vertical forces…