Find out who's locking the accounts

set lines 200
set pages 200

column USERNAME format a12
column OS_USERNAME format a12
column USERHOST format a25
column EXTENDED_TIMESTAMP format a40

SELECT USERNAME, OS_USERNAME, USERHOST, EXTENDED_TIMESTAMP
FROM SYS.DBA_AUDIT_SESSION WHERE returncode != 0 and username = '&Account_Locked'
and EXTENDED_TIMESTAMP > (systimestamp-1) order by 4 desc
/