Hello.

It's reproduced on all DB2 for LUW versions: 12.1, 11.5, 11.1.
I'm not able to open a Case with IBM Support, so I'd like someone to do it just because the technique used here could be useful for others...

Briefly:
Here is an example of DB2 package cache analysis.
Sometimes it's useful to group the entries for "similar" statements: the same statements with constants instead of parameter markers, the statements like 'in (?), in (?, ..., ?)', etc. All of them have the same values for (member, semantic_env_id, stmtid), but different stmt_text and other field values.
But it's convenient to show the statement text of whatever statement (just for referencd) in such a group along with aggregated metrics.

There is no ANY aggregation function in DB2, but it can be emulated with XMLROW & XMLAGG functions like in the example below, which one may run as is to look at the wrong result - the output rows are erroneously duplicated.  

But, if I uncomment the '--, M.XML_DOC' in the SELECT list or the '--WHERE X.STMT_TEXT IS NOT NULL' clause (these actions must not change the result set), I get the correct result.

SELECT 
  M.MEMBER, M.semantic_env_id, M.stmtid, M.num_diffferent_stmts
--, M.XML_DOC
, X.STMT_TEXT
FROM
(
  SELECT
      N.member, N.semantic_env_id, N.stmtid
    , COUNT(1) AS num_diffferent_stmts
    , XMLQUERY('$D[1]' PASSING XMLAGG(
        XMLROW(
                N.query_cost_estimate
              , N.stmt_text
        )
      ) AS "D") AS XML_DOC
  FROM TABLE
  (
    --MON_GET_PKG_CACHE_STMT(NULL, NULL, NULL, -2)
    SELECT *
    FROM
    (
      VALUES
          (0, 1, 1, 1, 'values 1')
        , (0, 1, 1, 2, 'values 2')
    ) T (member, semantic_env_id, stmtid, query_cost_estimate, stmt_text)
  ) N 
  GROUP BY N.member, N.semantic_env_id, N.stmtid
  HAVING COUNT(1) > 1
) M
CROSS JOIN XMLTABLE
(
  '$D/row' PASSING M.XML_DOC AS "D"
  COLUMNS
      QUERY_COST_ESTIMATE BIGINT   PATH 'QUERY_COST_ESTIMATE'
    , STMT_TEXT           CLOB(2M) PATH 'STMT_TEXT'
) X
--WHERE X.STMT_TEXT IS NOT NULL
ORDER BY M.member, M.semantic_env_id, M.stmtid

Here is a fiddle link to test.