I have instances where a simple START with where constraint is failing with 9D156 complaining there is an error near "AND"

The code is pasted below, but essentially we setup a where clause before executing the start

INTEGLOG_STATUS = 'C' AND INTEGLOG_SYSTEM =  'EDMS'

We are running in  a single thread so would not expect to need to LOCK THREAD and UNLOCK THREAD

either side of setting the where clause and doing the start.  Would using the LOACK THREAD help prevent 9D156?

...here is actual code

    INITIALIZE INTEGLOG-REC.
    MOVE 0 TO WS-COUNT-1

    MOVE "C" TO INTEGLOG-STATUS.
    MOVE "EDMS" TO INTEGLOG-SYSTEM.

* the following START has on 2 different occasions failed with 9D156

    PERFORM START-INTEGLOG-STATUS-SYSTEM-KEY
    IF WS-STATUS NOT = "00"
        EXIT PARAGRAPH
    END-IF.
          
*------------------------------------------          
 START-INTEGLOG-STATUS-SYSTEM-KEY.
*------------------------------------------
    PERFORM  SETUP-WHERE-CL-4-STATUS-SYSTEM-KEY.
   
    START INTEGRATION-LOG KEY NOT < INTEGLOG-STATUS-SYSTEM-KEY
              INVALID KEY
    MOVE "92" TO WS-STATUS.
   
    MOVE LOW-VALUES               TO A4GL_WHERE_CONSTRAINT.
   
   
   
*------------------------------------------
  SETUP-WHERE-CL-4-STATUS-SYSTEM-KEY SECTION.
*------------------------------------------
* this sets up the where clause   
        IF  INTEGLOG-STATUS = SPACE OR LOW-VALUES OR HIGH-VALUES OR ZERO 
            MOVE LOW-VALUES               TO A4GL_WHERE_CONSTRAINT
        ELSE
            MOVE SPACE                    TO A4GL_WHERE_CONSTRAINT
            MOVE 1                        TO WS-4GL-STR-PTR
            STRING
                   "INTEGLOG_STATUS = '"
                   INTEGLOG-STATUS
                   "'"
                 DELIMITED BY SIZE
                   INTO A4GL_WHERE_CONSTRAINT
                   WITH POINTER WS-4GL-STR-PTR
            END-STRING
 
            IF  INTEGLOG-SYSTEM = SPACE  OR LOW-VALUES OR HIGH-VALUES OR ZERO
                CONTINUE
            ELSE
                STRING
                       " AND "
                       "INTEGLOG_SYSTEM = '"
                       INTEGLOG-SYSTEM
                       "'"
                  DELIMITED BY SIZE
                      INTO A4GL_WHERE_CONSTRAINT
                      WITH POINTER WS-4GL-STR-PTR
                END-STRING
            END-IF
 
            INSPECT A4GL_WHERE_CONSTRAINT REPLACING TRAILING SPACES BY
                 LOW-VALUES
 
        END-IF.