Sounds like the second ? is not getting filled. I'm not sure that splunk will use every instance of the ?, so you'll need to rewrite your query.
However, as you want to limit your results to the 5 results after your checkpoint value, you could use the max_rows parameter in the db_inputs.conf file instead. Just use max_rows = 6 and change your query to be
SELECT A.* FROM "STG_CONTACT"."CRMTRC_CONVERSION_EVENT" A where A.CRMTRC_TIMESTAMP> ? order by CRMTRC_TIMESTAMP