What is the size of the file generally that are not getting uploaded ?
Also, on the local instance, are you using localhost:8000 to access the site or providing site_name:8000 ?
If the file size is larger, the file gets uploaded through socket-io which tries to resolve the file’s path. It fails to work for localhost:8000 as it will not find any site inside sites folder by that name. Try to store your site’s name in etc/hosts file and accessing it as site_name:8000.