NGINX crashes with 404 not found error - mysql

Question

I have ubuntu 14.04 and on the server I have nginx & mysql.
Everything works fine but after 5-10 requests to the API the nginx crashes.
The site has been loading for a long time ends up with 404 not found error.
When I restart the service service nginx restart my site is up again.
I have a strong server with
64GB Ram, 1Gbit Port 33TBMonth,
1TB Disk. 12Cores 24Threads.
I don't understand what's the error and how to solve it.
This is the nginx.conf:
https://pastebin.com/raw/eQtMSKAY
error log nginx:
2017/07/30 06:55:43 [error] 18441#0: *6302 connect()
to unix:/var/run/php5-fpm.sock failed (11: Resource
temporarily unavailable) while connecting to upstream,
client: XX.XX.XX.XX, server: 4107.150.4.82, request:
"GET /panel/ajax/user/tools/server?method=getstatus&port=25565 HTTP/1.1",
upstream: "fastcgi://unix:/var/run/php5-fpm.sock:",
host: "pay2play.co.il", referrer:
"http://pay2play.co.il/panel/panel?id=15"
2017/07/30 06:55:43 [error] 18441#0: *6302 open()
"/usr/share/nginx/html/50x.html" failed (2: No such file
or directory), client: 5.29.8.30, server: 107.150.44.82,
request: "GET /panel/ajax/user/tools/server?method=getstatus&port=25565 HTTP/1.1",
upstream: "fastcgi://unix:/var/run/php5-fpm.sock",
host: "pay2play.co.il", referrer:
"http://pay2play.co.il/panel/panel?id=15"

Answer 1

Based on what you pasted, the actual error is on the PHP side. The 404 is just nginx attempting to render a "nice" error page for the 503/4, contained in 50x.html. While your pasted version doesn't include it, it's likely contained in one of the includes (which are more relevant to the question than the top-level configuration shown here).
I expect there is something like (from the nginx docs actually):
error_page 500 502 503 504 /50x.html;