Missing delivery with the same vendor/delivery note not allowed

What causes this issue?

The shipment already contains a missing inbound delivery with this
data. A vendor - delivery note combination can only occur in a shipment
once as a missing inbound delivery.

System Response

The missing inbound delivery cannot be saved.

How to fix this error?

Check your entry.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.