In one of site collection at our SP2013 farm, we have "SharePoint Server Publishing" site feature and "SharePoint Server Publishing Infrastructure" site collection feature activated.
One of user (UserA) create a page (which is a custom content type page) in a page library. The new page is marked as "checked out by UserA". It is fine.
Then UserA open the page -> edit page -> key in something and "save". Then the page prompt him "The file Pages/subfolder/test001.aspx has been modified by i:0#.w|test\userA on 8Aug2014 xx:xx:xx" and ask him to choose "Leave this page" or "stay at this page". The date time is exactly the time userA was editing the page.
Whatever he choose, the update is saved and browser return to "View" mode (non-edit mode).
It is not the only problem. When userA want to edit the same page again and save, it prompt him that "The page could not be saved because your changes conflict with recent changes made by another user. If you continue, your changes will be lost."!
When userA choose continue or "check out". Follow screen show up: 
What can we do?