Retention in manufacturing is a cadence, not a campaign
Industrial customers do not churn with a cancellation. They drift. A second supplier is qualified for one part number, then two. A monthly schedule becomes fortnightly. A rate contract lapses and the next tender goes wide. Nobody sends an email saying they are leaving; the purchase orders simply get smaller and further apart until somebody in your sales review notices the account is half of what it was.
Which means the work is unglamorous and rhythmic: a weekly look at reorder gaps, a monthly look at volume against each account's own trailing average, a rolling contract calendar, and a quarterly conversation with the accounts that matter. Done properly it is the cheapest revenue a factory can protect, because the qualification, the tooling and the approvals have already been paid for.