Error in function module &2 for event &1

What causes this issue?

The function module &V2& called at event &V1& is incorrect.
CASE &V3&
WHEN '9'
In event 0602, an item that is not a credit memo was assigned.
WHEN '10'.
In event 0602, a credit memo was assigned to a payment with an
alternative business partner or contract account.
WHEN '11'.
In event 0602, the return table ET_ALLOCATION was filled incorrectly
(LFDNR_ITEM does not exist in T_ITEMS).
WHEN '12'.
In event 0602, the return table ET_ALLOCATION was filled incorrectly
(LFDNR_PAY does not exist in T_SUMS).
WHEN '12'.

System Response

The payment program continues; the action intended in the event is not
performed.

How to fix this error?

INCLUDE FICA_NA_OSS OBJECT DOCU ID TX

Error message extract from SAP system. Copyright SAP SE.