I've found the same problem with current stable Nginx-1.14.1 from nginx-repo on CentOS6.
There are two web-sites on this server, and problem occurs only on one of them.
Also I have many servers with nginx without this problem, so the problem may have some site-specific reasons, but I can't find any differences or strangeness in this environment.
The problem was resolved by installing Nginx-1.10.2 from epel repo.
There are two web-sites on this server, and problem occurs only on one of them.
Also I have many servers with nginx without this problem, so the problem may have some site-specific reasons, but I can't find any differences or strangeness in this environment.
The problem was resolved by installing Nginx-1.10.2 from epel repo.
