[otrs] Unabled to close a ticket

Hi, I have a ticket automatically re-opens by the user admin. It happened several times but only with one ticket. The ticket's history have this 3 lines at each time it's re-opened : Lock Ticket verrouillé. - root@localhost (Administrateur princ[..]) 24.07.2013 00:17:26 Misc Reset of unlock time. - root@localhost (Administrateur princ[..]) 24.07.2013 00:17:26 StateUpdate Avant : "closed successful" Après : "open" - root@localhost (Administrateur princ[..]) 24.07.2013 00:17:26 Can anyone help me ? Thanks and regards Claude