SAP Message V50R055 - Internal error within BAPI interface: The interface ID is not unique

Diagnosis
Internal error in BAPI interface: interface ID not unique.
When creating deliveries for a preceding document from another system,the request line identification in the REQUEST segment of therelevant BAPI interface is not unique.
A value in the REQUEST-ID field must only occur once in the entireREQUEST table.
This must be ensured by the caller, since this must not be changed inthe BAPI. It must not be changed, because this ID is used to create alink between the requested delivery item and the error log.