External identification for the delivery is not consistent

What causes this issue?

External Identification of delivery is not the same as stored. This
error occurs when the delivery being processed has a previous version in
the database but the external identification of the delivery varies.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.