Speculating but I think a production line has a rigid synchronized speed. If a step suddenly takes more time everything else must wait.
Imagine a queue of people at a buffet where overtaking is not allowed. If someone dawdles around at the juicer, people behind them need to wait while the salad bar is emptying and suddenly the cashier has nothing to do.
Imagine a queue of people at a buffet where overtaking is not allowed. If someone dawdles around at the juicer, people behind them need to wait while the salad bar is emptying and suddenly the cashier has nothing to do.