Hi! We're enjoying using your plugin, but have run into some trouble on our specific server setup with filenames including special characters, the configuration of which is unfortunately out of our control.
We could easily work around this by doing some additional sanitization to filenames on upload, if your plugin had a filter that allowed renaming the file. Would it be possible for you to add this functionality? No need to actually do any sanitizing yourself, just add an
$filename = apply_filters( 'wpfb_filename', $filename ) somewhere :)