DB2 Recursion Bill of Materials in SSRS issue with joining add'l tables

Bear with me - I'm rusty on SQL. Thanks! This yields an "LOPB or expression in select is invalid" when saving the dataset in SSRS.

WITH RPL (BPROD, BCHLD, BQREQ, LOPB) AS
(
	SELECT ROOT.BPROD, ROOT.BCHLD, ROOT.BQREQ, ILI.LOPB
	FROM BPCSFILE64.MBM ROOT, BPCSFILE64.ILI ILI
	WHERE ROOT.BPROD = ?
	AND ROOT.BCHLD = ILI.LPROD
UNION ALL
	SELECT PARENT.BPROD, CHILD.BCHLD, PARENT.BQREQ*CHILD.BQREQ, ILI.LOPB
	FROM RPL PARENT, BPCSFILE64.MBM CHILD, BPCSFILE64.ILI ILI
	WHERE PARENT.BCHLD = CHILD.BPROD
	AND CHILD.BCHLD = ILI.LPROD
)
	SELECT BPROD, BCHLD, (SUM(BQREQ) * ?) AS "Total QTY Used", LOPB
	FROM RPL
	GROUP BY BPROD, BCHLD
	ORDER BY BPROD, BCHLD