Upstream sent too big header while reading response header

The error will appear in Nginx error logs as:

* upstream sent too big header while reading response header from upstream, client: 10.20.30.40, server: localhost.example,

Update buffer sizes

Edit the nginx.conf file to update the buffer sizes:

server {
    fastcgi_buffers                 16  16k;
    fastcgi_buffer_size             32k;
    proxy_buffer_size               128k;
    proxy_buffers                   4 256k;
    proxy_busy_buffers_size         256k;
}