SAP Note 21109 - Error in calc. of interest on arr.: No WF_HZ_FUBAU

Symptom:

Runtime error in SAPLDUZI: Function module WF_HZ_FUBAU does not exist.

Cause and prerequisites

The function modules for the interest rate calculation are set dynamically. One call for credit interest rates and one for debit interest rates.
If only debit interest is needed for an interest indicator, only the debit interest rate module is filled in the entire program run. If in the course of the program run another interest indicator with credit interest is dealt with, the above error occurs.

Solution
In program RFDUZI01 in subroutine FORM DET_FB_INTEREST_RATE, deactivate the lines indicated with S11K* ('*' in the first position): FORM DET_FB_INTEREST_RATE.
*Bestimmung der Funktionsbausteine zur Zinssatzbestimmung
*--------------------------------------------------------------------
SELECT SINGLE * FROM T056L
WHERE INTTYP = 'SZ'.

IF SY-SUBRC NE 0.
ERR_TAB_T056L-FLAG = '1'.
PERFORM T056LFTAB_COLLECT(RFZINSS0) USING 'SZ'.
EXIT.
ENDIF.
WF-SZ_FUBAU = T056L-FUNCTBAU.

* IF T056U-FLAG3 = 'X'. "S11K*
SELECT SINGLE * FROM T056L
WHERE INTTYP = 'HZ'.
IF SY-SUBRC NE 0.
ERR_TAB_T056L-FLAG = '1'.
PERFORM T056LFTAB_COLLECT(RFZINSS0) USING 'HZ'.
EXIT.
ENDIF.
WF-HZ_FUBAU = T056L-FUNCTBAU.
* ENDIF. "S11K*
ENDFORM.

Then the program should run without problems.