I have a WordPress job portal and I need to accept various job offers and update a lot of posts.
When I try to accept or change posts, the site simple goes down and shows the error "502 bad gateway". It never happens before, it started to happen when I migrated to NGINX.

Someone can give some tips?

**Server Configuration:**

- OS: Ubuntu 18.04
- RAM: 16GB
- CPU: 6 Cores
- Disk: 100GB NVMe
- PHP: PHP7.3
- MYSQL: 10.5.6-MariaDB
- NGINX: Nginx 1.19.7
- REDIS: Redis 6.2.6
- opcache: yes

**++++++ nginx.conf**

user www www;
worker_processes auto;
error_log /www/wwwlogs/nginx_error.log crit;
pid /www/server/nginx/logs/nginx.pid;
worker_rlimit_nofile 51200;

events
{
use epoll;
worker_connections 51200;
multi_accept on;
}

http
{
include mime.types;
#include luawaf.conf;

include proxy.conf;

default_type application/octet-stream;

server_names_hash_bucket_size 512;
client_header_buffer_size 32k;
large_client_header_buffers 4 32k;
client_max_body_size 50m;

sendfile on;
tcp_nopush on;

keepalive_timeout 60;

tcp_nodelay on;

fastcgi_connect_timeout 1000;
fastcgi_send_timeout 1000;
fastcgi_read_timeout 1000;
fastcgi_buffer_size 64k;
fastcgi_buffers 4 64k;
fastcgi_busy_buffers_size 128k;
fastcgi_temp_file_write_size 256k;
fastcgi_intercept_errors on;

gzip on;
gzip_min_length 1k;
gzip_buffers 4 16k;
gzip_http_version 1.1;
gzip_comp_level 2;
gzip_types text/plain application/javascript application/x-javascript text/javascript text/css application/xml;
gzip_vary on;
gzip_proxied expired no-cache no-store private auth;
gzip_disable "MSIE [1-6]\.";

limit_conn_zone $binary_remote_addr zone=perip:10m;
limit_conn_zone $server_name zone=perserver:10m;

server_tokens off;
access_log off;

server
{
listen 888;
server_name phpmyadmin;
index index.html index.htm index.php;
root /www/server/phpmyadmin;
location ~ /tmp/ {
return 403;
}

#error_page 404 /404.html;
include enable-php.conf;

location ~ .*\.(gif|jpg|jpeg|png|bmp|swf)$
{
expires 30d;
}

location ~ .*\.(js|css)?$
{
expires 12h;
}

location ~ /\.
{
deny all;
}

access_log /www/wwwlogs/access.log;
}
include /www/server/panel/vhost/nginx/*.conf;
}

**++++++ fpm:**

[global]
pid = /www/server/php/73/var/run/php-fpm.pid
error_log = /www/server/php/73/var/log/php-fpm.log
log_level = notice

[www]
listen = /tmp/php-cgi-73.sock
listen.backlog = 8192
listen.allowed_clients = 127.0.0.1
listen.owner = www
listen.group = www
listen.mode = 0666
user = www
group = www
pm = dynamic
pm.status_path = /phpfpm_73_status
pm.max_children = 222
pm.start_servers = 30
pm.min_spare_servers = 30
pm.max_spare_servers = 60
request_terminate_timeout = 100
request_slowlog_timeout = 30
slowlog = var/log/slow.log

+++++++++ mysql.conf:

[client]
#password = your_password
port = 3306
socket = /tmp/mysql.sock

[mysqld]
port = 3306
socket = /tmp/mysql.sock
datadir = /www/server/data
default_storage_engine = InnoDB
performance_schema_max_table_instances = 400
table_definition_cache = 400
skip-external-locking
key_buffer_size = 256M
max_allowed_packet = 100G
table_open_cache = 1024
sort_buffer_size = 4M
net_buffer_length = 4K
read_buffer_size = 4M
read_rnd_buffer_size = 256K
myisam_sort_buffer_size = 64M
thread_cache_size = 128
query_cache_size = 128M
tmp_table_size = 128M
sql-mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

#skip-name-resolve
max_connections = 500
max_connect_errors = 100
open_files_limit = 65535

log-bin=mysql-bin
binlog_format=mixed
server-id = 1
expire_logs_days = 10
slow_query_log=1
slow-query-log-file=/www/server/data/mysql-slow.log
long_query_time=3
#log_queries_not_using_indexes=on


innodb_data_home_dir = /www/server/data
innodb_data_file_path = ibdata1:10M:autoextend
innodb_log_group_home_dir = /www/server/data
innodb_buffer_pool_size = 1024M
innodb_log_file_size = 512M
innodb_log_buffer_size = 128M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50
innodb_max_dirty_pages_pct = 90
innodb_read_io_threads = 6
innodb_write_io_threads = 6

[mysqldump]
quick
max_allowed_packet = 500M

[mysql]
no-auto-rehash

[myisamchk]
key_buffer_size = 256M
sort_buffer_size = 4M
read_buffer = 2M
write_buffer = 2M

[mysqlhotcopy]
interactive-timeout

**++++++ error log**:

2022/02/22 14:24:12 [error] 1095#0: *39359 open() "/www/wwwroot/site.com/.well-known/traffic-advice" failed (2: No such file or directory), client: 172.70.xx.xx, server: site.com, request: "GET /.well-known/traffic-advice HTTP/1.1", host: "site.com

**++++++ php.ini**:

max_execution_time: 100
max_input_time: 100
memory_limit: 512
post_max_size: 200M
upload_max_filesize: 150M
max_file_uploads: 200
default_socket_timeout: 60