find the below error message in nginx error log: upstream sent too big header while reading response header from upstream
add the three rows to http and server section
fastcgi_buffer_size 256k;
fastcgi_buffers 32 256k;
fastcgi_busy_buffers_size 256k;
add the three rows to php proxy:
fastcgi_buffer_size 256k;
fastcgi_buffers 4 256k;
fastcgi_busy_buffers_size 256k;