We have a customer who has had an incorrect address in our system for ... a long while, now. Each time we shipped, UPS would flag the package, correct the ZIP code, and forward it along. This slowed the shipment by a day.
They've never ordered things that were urgent or time-sensitive, so it was never an issue before.
Tuesday, we shipped some things to them that they needed today.
Wrong ZIP code + holiday rush = two packages (out of three) arriving. The other one will show tomorrow. Too late.