Enum code meaning changed mid-migration

A migration renames the status enum on a shipments table: the integer code 3 changed meaning from 'in_transit' to 'delivered' (and a new code 5 now means 'in_transit') to match a new carrier API. The producer service was deployed with the new mapping at 14:00. By 14:30 customers get 'your package was delivered' emails and SMS for packages still in transit, and a partner webhook is firing 'delivered' events early. Dashboards: error rate flat, throughput normal. Some downstream consumers were NOT redeployed. How do you triage, stop the wrong notifications, and reconcile state?