Can I get FTP access and a url to reproduce? It looks like a folder permissions issue, but it could be a path issue in general. It looks like the code isn't handling the ../ in the upload path properly. You could probably fix it by just using a root relative path on line 14 like:
'UploadFolder' => "/docs/",
But you may have to adjust the permissions on the docs folder to give it read/write privileges.