Audit Trail 11g XML tag <Client_ID> empty

Hi,

i have wierd problem with field "CLIENT_ID" as when we've had audit trail set to DB we got this field populated by application user (as it should be) name however after switching over to XML this tag is missing from XML audit log files. Both V$Session and (ex) db_audit_trail table have this field populated so it should be working application/oracle wise.  Ofcourse view V_$XML_AUDIT_TRAIL has this field "null".

I don't have any special auditing policies setup everything is by default as our primary auditing tool is IBM Guardium and this application tag works. I'm exploring options of removing IBM tool and use Oracle natives auditing but so far this issue is kind of killing this option as we really need appuser to be audited.