Nginx reverse proxy 504 gateway timeout only happen in browser access - nginx

Question

I used Nginx as a reverse proxy and when I access the url from the browser (Chrome, Firefox) it will show 504 gateway timeout. But when I use curl or wget to access the url, it works fine. It is really a weird issue, can anyone give me some help?
Following is my configuration: https://pastebin.com/fZHEtRGa
The upstream configuration is:
upstream default-nginx-z-80 {
# Load balance algorithm; empty for round robin, which is the default
least_conn;
keepalive 32;
server 10.1.228.195:80 max_fails=0 fail_timeout=0;
}
The server configuration is
server {
server_name z-ingress.mixhub.cn ;
listen 80;
listen [::]:80;
set $proxy_upstream_name "-";
location / {
port_in_redirect off;
set $proxy_upstream_name "default-nginx-z-80";
set $namespace "default";
set $ingress_name "nginx-z";
set $service_name "";
client_max_body_size "1m";
proxy_set_header Host $best_http_host;
# Pass the extracted client certificate to the backend
proxy_set_header ssl-client-cert "";
proxy_set_header ssl-client-verify "";
proxy_set_header ssl-client-dn "";
# Allow websocket connections
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "";
proxy_set_header X-Real-IP $the_real_ip;
proxy_set_header X-Forwarded-For $the_real_ip;
proxy_set_header X-Forwarded-Host $best_http_host;
proxy_set_header X-Forwarded-Port $pass_port;
proxy_set_header X-Forwarded-Proto $pass_access_scheme;
proxy_set_header X-Original-URI $request_uri;
proxy_set_header X-Scheme $pass_access_scheme;
# Pass the original X-Forwarded-For
proxy_set_header X-Original-Forwarded-For $http_x_forwarded_for;
# mitigate HTTPoxy Vulnerability
# https://www.nginx.com/blog/mitigating-the-httpoxy-vulnerability-with-nginx/
proxy_set_header Proxy "";
# Custom headers to proxied server
proxy_connect_timeout 5s;
proxy_send_timeout 60s;
proxy_read_timeout 60s;
proxy_redirect off;
proxy_buffering off;
proxy_buffer_size "4k";
proxy_buffers 4 "4k";
proxy_request_buffering "on";
proxy_http_version 1.1;
proxy_cookie_domain off;
proxy_cookie_path off;
# In case of errors try the next upstream server before returning an error
proxy_next_upstream error timeout invalid_header http_502 http_503 http_504;
proxy_pass http://default-nginx-z-80;
}
}