Hi. I had this problem already in 1.8.x. It only happens with a couple of customers from China. Everytime they reply by mail to a ticket, a new ticket is created instead of adding the response to the existing ticket.Is it a known issue? Should I open a bug report in the repo? Whatever I can do to help you chase the issue, please let me know. I have the emails if you want me to send you the source of any of them.Thanks in advance!