XF 1.3 Problem with some topic

Hello ,

I have a problem with XenForo 1.3 :
On some topic, we can not post reply , we have a error :

Cannot insert a message in the middle of a discussion.
XenForo_DataWriter_DiscussionMessage->_setPosition() inXenForo/DataWriter/DiscussionMessage.php at line 353
XenForo_DataWriter_DiscussionMessage->_preSave() in XenForo/DataWriter.php at line 1446
XenForo_DataWriter->preSave() in XenForo/ControllerPublic/Thread.php at line 542
XenForo_ControllerPublic_Thread->actionAddReply() in XenForo/FrontController.php at line 347
XenForo_FrontController->dispatch() in XenForo/FrontController.php at line 134
XenForo_FrontController->run() in /var/www/index.php at line 13

How can I fix this?
Ps: Sorry for my translation i'm french

Your server time would be set on the server itself; and shouldn't have been changed via the coding.
So just this solution? because I tried two solutions, but there are always errors

I assume you're on a shared server. Contact your webhosting company and ask them to look at the server time. Explain the problem you are having.
I'm on a VPS