Tonif4

Hi, I run Whmcs 5.2.7 and during the past week, my clients started having an issue by seeing the tickets already oppened or closed (they still can open new tickets, though). I have whmcs installed on this directory domain.com/central. When they go to domain.com/central/supporttickets.php/viewticket.php to view the tickets, everything's ok. When they click in the title of one of them or in the "View Ticket" button, they are redirected, in one of the cases, to this page: http://www.domain.com/central/viewticket.php?tid=563003&c=6PNwfo09, that shows an 404 error page. How can I solve this problem? thanks!