Every operational problem gets explained before it gets measured. Someone walks the floor, sees the queue, and forms a view and because the view is reasonable, it hardens into fact long before anyone checks it.
The way out isn't more data. It's one question, asked early: does this get worse when we get busier? A capacity problem does. A process problem doesn't. That single test separated three years of assumption from the actual answer in an afternoon.
The queue was visible to everyone. The reason for it was visible to nobody, because it lived in a scan that wasn't happening — and absence doesn't show up on a walk round the plant.
Most operational problems have a version of this hiding in them: a step nobody owns, a loop that looks closed and isn't. It rarely shows up in a process map, because on paper the step exists. It only shows up when you measure what happened, truck by truck, and notice that a number is impossible.
If you're carrying a queue that nobody can explain, the first question isn't “how much capacity do we need?” It's “does the wait get worse when we get busier?” If the answer is no, you're not looking at a capacity problem and you'd want to know that before you build anything.