Computers with business logic. It can't be the same one if it travels faster than is possible. And anyway, if they were being tracked ...
What are you going to use, a laptop or something?
If it ran out of power without completing its process, upon reboot it might very well assign the same number to the next container.
Even without a computer, you could have the day shift actually paint the number on the first container, but fail to finish the paperwork or it could get lost.
Then the night shift comes along and uses the same number on the next container.