Thanks for concern, actually it's my user report the problem, I don't know exactly what happened when he post message.
I try to follow the you guys provide, but it seems all doesn't work. So I try to delete some messages under this topic and reply some new messages, after that it seems come back to normal.
I think maybe the problem it's about the "sync", certainly I don't know your system structure very well.
For our forum, most of our users are chinese people, so I set the default language is Chinese, maybe it will bring you some inconvenience.