Hello,
How are you trying to upload the files? From the backend or from the frontend (by using the front office publishing add-on?).
The Copy from FTP method might probably suits your needs in your case.
Copy from FTP folder (advanced mode): to do this, we need to use an FTP client (e.g. Filezilla) to drop files into a directory defined in the WP Customer Area settings. Note that this method is particularly useful for large files and is better suited for advanced users
Regards.