Why is a part of the Wordpress site scripts not loaded when accessing the site through a proxy?

Question

cloudflare

Part of the site's Wordpress scripts are not loaded when accessing through a proxy to a site that works through Cloudflare,

for example domain.ru/wp-includes/js/mediaelement/mediaelement-and-player.min.js?ver=4.2.16 gives a 522 error after about seconds 10-20
However, if I access from the IP address of the home provider, then the download occurs.
Is Cloudflare blocking or the server? I whitelisted my IP iptables -I INPUT -p tcp -m multiport --dports http,https -s 1.1.1.1 -j ACCEPT