in almost all of the cases we investigated of this issue occurring, the cause of problem came down to the site definition.
specifically the settings for the testing server.
In almost every case, the problem was in using the remote FTP Server as the testing server, and not setting the host directory section correctly. On some servers, the remote directory can be left blank. On other servers, the remote directory needs to point to the public_html/ folder, the root folder of your web site.
to determine if the remote directory needs to be set, use an FTP tool like FileZilla to connect to your sites ftp server.
If you see a folder named public_html or htdocs at the root of the server, then that needs to be entered as the Remote Directory in your site definition. IF you see the websites index.php file and other web files at the root, the Remote Directory setting can be left blank.