duplicate record error when updating a physical file

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I get an error when I try to update a physical file.  The error is---> "Attempt 
to write a duplicate record to file CDEBP"......"RPG procedure detected an 
output record with a duplicate key field"

Can anyone see why I'd be getting this error?



*duplicate record error when updating CDEBP
F CDEBP     UF A E           K DISK

 *
 *  Get Record
C     CDEB_KEY02    CHAIN        CDEBP

 *
 * Make sure Record is NOT in CTRNP file
C      CTRN_KEY01    SETLL     CTRNP1
C                                   IF              %FOUND(CTRNP1)
C                                   EVAL        CTRNP_FLG = 'Y'
C                                   ELSE
C                                   EVAL        CTRNP_FLG = 'N'
C                                   ENDIF

 * Move Account "A" record into save fields
C                                  IF                 CTRNP_FLG = 'N'
C                                  EVAL          MVEFLG = '01'
C                                  EXSR          MOVE_DATA
 * Move saved Account "B"  record into Account "A" fields
C                                  EVAL          MVEFLG = '02'
C                                  EXSR          MOVE_DATA
C                                  UPDATE    CDEB
C                                  ENDIF

 C     *INZSR               BEGSR

C     CTRN_KEY01    KLIST
C                                  KFLD                    KF_ALP2
C                                  KFLD                    KF_NUM2
 *
C     CDEB_KEY01    KLIST
C                                  KFLD                    KF_ALP1
C                                  KFLD                    KF_NUM1
C                                  ENDSR


*Physical File DDS
A                                              UNIQUE
A          R CDEB
A              RP1ALP         5
A              RP1NUM       5S 0
A              BLA1            15
A              BLA2            10
A          K RP1ALP
A          K RP1NUM


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