Sorry to rub salt in a wound, but moving a loose load (and unwrapped interlocked boxes that tall are still "loose" since they can (and did) collapse
*) that is stacked above handle hight of a pallet truck is asking for trouble.
As my father sagaciously always said: Don't break your back or your heart. If you overload, something will break. Take two trips.
* This is even
mentioned by OSHA (my highlight): "Bags, containers, bundles, etc. are stored in tiers that are stacked, blocked, interlocked and
limited in height so that they are stable and secure to prevent sliding or collapse."