VPN and cache are different things. Cache’s purpose is to speed up the use of the Internet and save bandwidth. For example, Elisa offers its customers a cache.
Without cache, for example, from an Asian remote server, web pages, images and other files are downloaded at a rate of 0.5 Mbps. When the connection passes through the cache, the files remain in the carrier cache once they are loaded.
In the following download times, the files will be found on the cache and will be downloaded for example at full speed, e.g. 100 Mbps. Https connections do not allow cachets.
What Is Cache?
Caching proxy nowadays has great benefits in itself. Today, service providers in the near future could use CDN services to bring these images closer. Proxy miniature is not in itself a solution when it is not used in Finland.
I would recommend that you be connected to the web site administrator and be absolutely sure that you are using the CDNs. CDNs work well with HTTP than HTTPS and benefit all users when CDN servers are on most server slots.
A proxy Chrome does not have a problem in proxysite, and not in older Firefox’s if the site requires login.
For Firefox 51 and 52, the problem might appear on the work reasonably on Chrome but not on Firefox.