 <p>Found this while looking for same answer, it seems to be a windows + Doctrine issue</p> <p><a href="http://www.doctrine-project.org/jira/browse/DDC-2210">Doctrine Ticket with more detailed info</a></p> <p>TLDR: Basically the proxy is trying to rename a file thats still being used, works in linux but not always on windows.</p>