The containers aren't physically checked around the world, as a rule.
Their paperwork is. They're sealed with a Government locking-'band'. The weight of the container has to logically match-up with the items listed inside.
When it's opened at the address on the paperwork, some countries might have a few officials on site. That's about it. But using one to travel in is like being locked in a 20x8x8 windowless submarine for 2-months.