[otrs] Ticket re-opened by system

Hi, For one ticket, every night it's re-open by system. I close it and then the next night, I have this lines are in history : Lock Ticket verrouillé. - root@localhost (Administrateur princ[..]) 26.04.2016 00:10:04 Misc Reset of unlock time. - root@localhost (Administrateur princ[..]) 26.04.2016 00:10:04 StateUpdate Avant : "closed successful" Après : "open" - root@localhost (Administrateur princ[..]) 26.04.2016 00:10:04 I do not know where to look If someone had an idea ? Thanks and regards Claude