FastCGI cache on NGINX causes blank screen in pages

I have the exact same configurations for my other NGINX server with Porto theme and this never happens. Please review my settings and advise:

fastcgi_cache_path /var/cache/nginx/fastcgi_temp/ levels=1:2 keys_zone=WORDPRESS:200m max_size=10g inactive=60m use_temp_path=off;
fastcgi_cache_key "$scheme$request_method$host$request_uri";

server {
	listen 443 ssl ;
	http2 on ;
	listen [::]:443 ssl ;
	server_name jmic.co.kr www.jmic.co.kr; # managed by Certbot
	ssl_certificate /etc/letsencrypt/live/jmic.co.kr/fullchain.pem; # managed by Certbot
	ssl_certificate_key /etc/letsencrypt/live/jmic.co.kr/privkey.pem; # managed by Certbot

	root /var/www/html/;
	index index.php;

	# set max upload size
	client_max_body_size 2G;
	fastcgi_buffers 64 4K;

	access_log /var/log/nginx/wordpress_https_access.log combined;
	error_log /var/log/nginx/wordpress_https_error.log;

	server_tokens off;

 	# START FastCGI
	# POST requests and urls with a query string should always go to PHP
	if ($request_method = POST) {
	    set $skip_cache 1;
	}
	
	if ($request_method = PATCH) {
	set $no_cache 1;
	}
	
	if ($query_string != "") {
	    set $skip_cache 1;
	}   
	
	# Don't cache uris containing the following segments
	if ($request_uri ~* "/wishlist/|/my-cart/|/checkout/|/my-account/|/wp-admin/|/xmlrpc.php|wp-.*.php|^/feed/*|/tag/.*/feed/*|index.php|/.*sitemap.*\.(xml|xsl|html)") {
	    set $skip_cache 1;
	}   
	
	# Don't use the cache for logged in users or recent commenters
	if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
	    set $skip_cache 1;
	}
	# END FastCGI

	# BEGIN CompressX
	set $ext_avif ".avif";
	if ($http_accept !~* "image/avif") {
	  set $ext_avif "";
	}

	set $ext_webp ".webp";
	if ($http_accept !~* "image/webp") {
	  set $ext_webp "";
	}

	location ~ /wp-content/(?<path>.+)\.(?<ext>jpe?g|png|gif|webp)$ {
	  add_header Vary Accept;
	  add_header Cache-Control "private";
	  expires 365d;
	  try_files
	    /wp-content/compressx-nextgen/$path.$ext$ext_avif
	    /wp-content/compressx-nextgen/$path.$ext$ext_webp
	  $uri = 404;
	}
	# END CompressX

	##
	# BEGIN Nginx Bad Bot Blocker Includes
	# REPO: https://github.com/mitchellkrogza/nginx-ultimate-bad-bot-blocker
	##

	include /etc/nginx/bots.d/ddos.conf; 
 	include /etc/nginx/bots.d/blockbots.conf;
 	# END Nginx Bad Bot Blocker Includes

	include /etc/nginx/site-extras/*.conf;

	location = /favicon.ico {
		log_not_found off;
		access_log off;
	}

	location = /robots.txt {
		allow all;
		log_not_found off;
		access_log off;
	}

	location / {
		try_files $uri $uri/ /index.php?$args ;
	}

	location ~* \.(htaccess|htpasswd) {
		deny all;
	}

	location ~* \.(?:ini|conf|txt)$ {
		deny all;
	}

	location ~ \.php(?:$|/) {
		fastcgi_split_path_info ^(.+\.php)(/.+)$;
		include fastcgi_params;
		fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
		fastcgi_param PATH_INFO $fastcgi_path_info;
		fastcgi_param HTTPS on;
		fastcgi_pass 127.0.0.1:9000;
		fastcgi_read_timeout 60s;

		# START FastCGI configurations
		fastcgi_cache WORDPRESS;		
		fastcgi_cache_valid 200 301 302 60m;
		fastcgi_cache_use_stale error timeout updating invalid_header http_500 http_503;
		fastcgi_cache_min_uses 1;
		fastcgi_cache_lock on;
		fastcgi_cache_bypass $skip_cache;
		fastcgi_no_cache $skip_cache;
		fastcgi_ignore_headers Cache-Control Expires Set-Cookie;
		add_header X-FastCGI-Cache $upstream_cache_status;
		# END FastCGI configurations
	}

	## START SEOPress sitemap location
	location ~ (([^/]*)sitemap(.*)|news|author|video(.*))\.x(m|s)l$ {
		rewrite ^.*/sitemaps\.xml$ /index.php?seopress_sitemap=1 last;
		rewrite ^.*/news.xml$ /index.php?seopress_news=1 last;
		rewrite ^.*/video([0-9]+)?.xml$ /index.php?seopress_video=1&seopress_paged=$1 last;
		rewrite ^.*/author.xml$ /index.php?seopress_author=1 last;
		rewrite ^.*/sitemaps_xsl\.xsl$ /index.php?seopress_sitemap_xsl=1 last;
		rewrite ^.*/sitemaps_video_xsl\.xsl$ /index.php?seopress_sitemap_video_xsl=1 last;
		rewrite ^.*/([^/]+?)-sitemap([0-9]+)?.xml$ /index.php?seopress_cpt=$1&seopress_paged=$2 last;
	}
	## END SEOPress sitemap location

	#START Staging Site SSL location
	location /dev {
		# First attempt to serve request as file, then
		# as directory, then fall back to displaying a 404,
		#try_files $uri $uri/ = 404;
		try_files $uri $uri/ /dev/index.php?$args;
	}
	#END Staging Site SSL location

	# set long EXPIRES header on static assets
	location ~* ^.+\.(?:css|js|eot|otf|ttf|woff|woff2|svg|font.css)$ {
		expires 30d;
		access_log off;
	}

	#CDN CORS policy font fix
	location ~* \.(css|js|eot|otf|ttf|woff|woff2|svg|font.css)$ {
		add_header Access-Control-Allow-Origin *;
	}

	# Rocket-Nginx configuration
	include rocket-nginx/conf.d/default.conf;
}