As with many things that have a percentile failure mode, it's almost always cheaper to build something flexible that can handle issues than it is to design a perfect widget that never fails.

This is where humans came in in autonomation, the toyota version of automation. When you try to eliminate adaptability and adjustment entirely, the whole system becomes only metastable / fragile.

Is the human doing anything flexible here? It isn't like they occasionally unclog packages plus a dozen other things. They are on the line to just unclog the packages. Likewise for most other factories. When you see clips of the human in the line, they are just doing some task someone has not made a machine for yet. There is no specific human input required here. No human touch. They are doing things like turning over the object because no one designed a flipper to turn it over yet. Mindless repetitive tasks.