I work at the Worldport Hub and the NatGeo youtube video essentially does a good job of showing what goes on there.
The good thing about its size is that there are hundreds of different jobs you can do there if you get bored doing one thing, or just want to transfer to another building.
Missorts largely depend on the type of building you're in. The older ones tend to have far less missorts than the newer ones. In the old buildings, things come down one belt and there are a row of cans or feeders on each side stretching the length of the belt. As packages come down, you have to see which package is yours and manually scan it into your corresponding load.
In the newer buildings, there are belts/ and or chutes that go into each individual can or feeder, so the packages usually divert to the right load. However since you don't have to manually scan in the package, potential missorts can happen since people don't bother to look at the label to see if it's correct.