Two-label habit paid off. A vial came through where the printed label and my own inventory tag disagreed on the compound. Because I cross-check the COA, the vial label, and my own tag before anything gets reconstituted, the mismatch jumped out immediately.
Stopped, photographed everything, confirmed against the batch on the COA, sorted it. The lesson isn't "labels are bad" — it's that a 30-second cross-check at intake catches the thing you'd otherwise discover three steps too late.