P1 checkout incident: a stale paymentType blocked PayPal initialization

Situation

A customer reported a broken PayPal payment link. An external provider issue was a plausible first hypothesis, but the initial task was to reconstruct the application's own checkout state. With the retailer Net 30 feature in place, the client could retain an older payment type that no longer appeared in the authorized options for that particular buyer.

Approach

We traced the Unsupported payment type failure to a stale paymentType reaching checkout before PayPal initialization. The fix normalizes the current selection against the authorized payment methods: consumer checkout falls back to PayPal, while eligible retailer Net 30 remains valid. We added the case to checkout smoke regression coverage and prepared a controlled production hotfix.

Outcome

An invalid historical payment choice no longer prevents ordinary PayPal checkout initialization. The patch preserves retailer payment terms instead of disabling a separate business flow. The fix was deployed and checked in production.