Node.js on nginx + Cent OS7 shows blank page or ERR_TOO_MANY_REDIRECTS - node.js

Question

Symptom
I think I've messed up my domain/nginx settings. The server shows up properly for 70~60% of time but sometimes it shows blank page(no html at all) or ERR_TOO_MANY_REDIRECTS page.
the url is: sungryeol.com
I've checked both Stackoverflow and Node.js + CentOS 7 + nginx setup tutorials on Google(which leads to digital ocean mostly)
Settings
Node.js / Express.js
OS: Cent OS 7(Vultr VPS)
Reverse proxy: nginx
DNS: Namecheap
Namecheap domain setting
Type------------------Host---Value-------------------------------TTL
A Record--------------#------45.32.9.128-------------------------5 min
CNAME Record----------www----sungryeol.com.----------------------5 min
URL Redirect Record---www----http://www.sungryeol.com Unmasked---
the dot on sungryeol.com'.' is automatically added by Namecheap UI.
nginx setting
nginx -t shows the configuration has no error. The internal setting has no problem I assume. It works fine with IP address but still shows blank page or redirect error from the URL : (www).sungryeol.com.
/etc/nginx/conf.d
server {
listen 80;
server_name localhost;
#charset koi8-r;
#access_log /var/log/nginx/host.access.log main;
location / {
root /usr/share/nginx/html;
index index.html index.htm;
}
#error_page 404 /404.html;
# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/share/nginx/html;
}
...
}
/etc/nginx/nginx.conf
user nginx;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
#tcp_nopush on;
keepalive_timeout 65;
#gzip on;
#include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-available/*.conf;
}
/etc/nginx/sites-available/portfolio.conf
upstream portfolio {
server 127.0.0.1:3001 max_fails=0 fail_timeout=10s weight=1;
ip_hash;
keepalive 512;
}
server
{
listen 80;
listen [::]:80 ipv6only=on default_server;
server_name sungryeol.com www.sungryeol.com;
keepalive_timeout 10;
# client_max_body_size 50M;
index index.html;
location /
{
proxy_pass http://portfolio;
include /etc/nginx/proxy_params;
}
}
/etc/nginx/proxy_params
proxy_buffers 16 32k;
proxy_buffer_size 64k;
proxy_busy_buffers_size 128k;
proxy_cache_bypass $http_pragma $http_authorization;
proxy_connect_timeout 59s;
proxy_hide_header X-Powered-By;
proxy_http_version 1.1;
proxy_ignore_headers Cache-Control Expires;
proxy_next_upstream error timeout invalid_header http_500 http_502 http_503 htt$
proxy_no_cache $http_pragma $http_authorization;
proxy_pass_header Set-Cookie;
proxy_read_timeout 600;
proxy_redirect off;
proxy_send_timeout 600;
proxy_temp_file_write_size 64k;
proxy_set_header Accept-Encoding '';
proxy_set_header Cookie $http_cookie;
proxy_set_header Host $host;
proxy_set_header Proxy '';
proxy_set_header Referer $http_referer;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Original-Request $request_uri;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";