Android app stuck on "Waiting for Server Connection"

[playpeace]

Hosting RocketChat, configured via Docker and running in sub-directory /chat using Nginx.

Able to access via Web and browser in mobile but not via the RocketChat Android app (Rocket Chat, Rocket Chat+ etc), haven't tried ios.

Not set up for SSL, only http requests (and hopefully websockets) as mentioned here: https://rocket.chat/docs/installation/manual-installation/configuring-ssl-reverse-proxy/

Part of Nginx config file

server{
    listen 80
    .
    .
    location ^~ /chat/ {
        proxy_pass http://127.0.0.1:8096/chat/;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header Host $http_host;

        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forward-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forward-Proto http;
        proxy_set_header X-Nginx-Proxy true;

        proxy_redirect off;
	client_max_body_size 200M;
    }

The Rocket.Chat app downloads files and then gets stuck in a loop (Much similar to the comment at the end by @takigama at #108)

Any ideas?