When a file is being uploaded through the form, and the filename is non-latin (in my case, Greek), the plugin sanitises the filename (for example if it has a name ΤΕΣΤ123.DOCX, it saves on disk as 123.DOCX). If the file is uploaded with latin characters, it saves correctly the filename.
This bug is only experienced with the plugin, for example the native wp media library uploads correctly.
We’re on WP 4.7.4, PHP 7.0 and IIS 8 on Windows server 2012.