What is the cause of the 500 (nginx) error on a clean install of WordPress?

Question

Nginx

I have an NGINX server with several WordPress sites powered by CloudFlare.
On all sites, an error periodically pops up (screenshot).
This particular screen is made on a clean, freshly installed WordPress.
The server meets the official requirements for WP sites:
https://www.nginx.com/resources/wiki/start/topics/...
What could be the reason for the errors?

Answer 1

1) Path (does not find the file, more likely)
2) Permissions (less likely, but also possible)
3) Error in php (in pure WP, the reason may not be here)

Answer 2

You need to look at the php and web server logs - everything is written there.