When starting up the standalone 1.4.3 version, during the upgrade, it fails during DuplicateNotificationsCleanupUpgradeTask. MySQL complains about syntax error with one of the SQLs being run. I believe the SQL is:

select grouped_data.PAGEID, grouped_data.SPACEID, grouped_data.USERNAME from ( select count as NOTIF_COUNT, PAGEID, SPACEID, lower(USERNAME) as USERNAME from NOTIFICATIONS group by lower(USERNAME), PAGEID, SPACEID ) grouped_data where grouped_data.NOTIF_COUNT > 1

At the very least, please test your upgrades on MySQL which is probably the most common db used for Confluence.