Requisition Report errors when filtering to one BU

We have a Requisition Approved Status report that runs a report for approved Reqs for our 3 Business Units, Report runs fine when ALL BUs are selected or even 2 BUs. But when we select just 1, the report give a Invalid Number error. SQL code for the report is below. Anyone have idea and what we can change to prevent the error.

SELECT
HOU.NAME REQUISITION_BU_NAME,
HOU.ORGANIZATION_ID,
PRH.REQ_BU_ID,
PRH.REQUISITION_NUMBER,
PRH.DESCRIPTION,
PREPARER.FULL_NAME ENTERED_BY,
--trunc(PRH.CREATION_DATE) CREATION_DATE,
to_char(PRH.CREATION_DATE, 'DD-Mon-YYYY','NLS_DATE_LANGUAGE=AMERICAN') CREATION_DATE,