I’m not sure if there is a way to be honest. If the language is not marked in polylang, then it can be either untranslated or in the root language. So if the plugin was to include items, where no translations were found in the current language, then it may include items added in all of the other languages. Sort of a catch-22 situation.
If you want, you can add temporary FTP access, and I can try something via custom code, but I can not guarantee anything unfortunately.