Foraml error in table FKKOP: Field OPUPW or OPUPZ not first

What causes this issue?

When you <ZH>create a document</> in Contract Accounts Receivable
you must ensure that the fields <DS:DE.OPUPW_KK>repetition item</>
(OPUPW_KK) and <DS:DE.OPUPZ_KK>sub-item</> (OPUPW) are empty. OPUPW is
filled when you delete a repetition item; OPUPZ is filled when you
partially clear an item.

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?

INCLUDE NA_SYSADMIN1 OBJECT DOKU ID TX

Procedure for System Administrators

INCLUDE FICA_NA_OSS OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.