Replace Resources with Nginx Reverse Proxy

Question

English is not my native language, so I use a translator. My questions may be a little difficult to understand, I hope you can understand.
I want to access B.com, but B.com is blocked and I can't access it directly. So I set up a reverse proxy server. A.com points to my reverse proxy server, while B.com points to the source server. My reverse proxy server is configured like this.

server
{
    listen 80;
    listen 443 ssl http2;
    server_name A.com;

    location /
  {
    proxy_pass https://B.com;
    proxy_set_header Host B.com;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header REMOTE-HOST $remote_addr;
  }
    *other configurations*
}

However, some of the resources on the page are from www.B.com and are also blocked. So I added the following configuration.

sub_filter "B.com" "A.com";
sub_filter_types *;
sub_filter_once off;
proxy_set_header Accept-Encoding "";

This successfully replaced most of the content, but some of it did not. What should I do? Please help me ;(