SAP Message VN351 - Object type & is assigned to the header in application &

Diagnosis
You have entered a business object type (&V1&) consistent to the item inthe application document of application &V2&.

System Response
In system table T681Z a business object type is assigned to both theheader and the item of the application document of application &V2&.You can enter any of the object types from the business objectrepository, which have a key structure consistent with that of one ofthe object types.

Procedure
Make sure that the condition is related to an item in the applicationdocument from application &V2&.