Double CO object in row & copied to the planning data interface

What causes this issue?

Within the modules of the planning data interface, a record exists more
than once in table IRKU01* or IRKU02*. The error occurs in row &v1& of
the table.

System Response

The first row is updated correctly. All further rows with the same
Controlling object are ignored.
The respective incorrect records are not returned but just ignored.

How to fix this error?

Check the function module callup. Check which record is correct, and
remove the other record before the callup.

Error message extract from SAP system. Copyright SAP SE.