How I unstuck an Amazon FBA shipment stuck in receiving over carton labels

I ran into this in a marketplace operation sending mixed-SKU cartons into Amazon FBA. The issue was a shipment sat in receiving with several cartons not checked in. At first I blamed Amazon warehouse delay, but it showed up whenever the team relabeled cartons after a last-minute carton count change. This caused inventory was unavailable during a promotion and ad spend kept running, so I treated i…