Track error in IS jobs

hi team,

today again i checked one of my jobs failed due to error

[E] 2016-01-19 23:05:24.461 Executing SQL: INSERT INTO ISREP.MMT_Lock(lock_id,object_id,table_id,object_lock,expires,machine,process) ..........

[E] 2016-01-19 23:05:24.467 ORA-00001: unique constraint (ISREP.MMT_U_LOCK) violated

[E] 2016-01-19 23:05:24.477 java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (ISREP.MMT_U_LOCK) violated

Usually this happens, if there is a wrong source record coming from the source system but how can I check like hoe can I track?? I am not getting any idea..