This problem may occurs because of a configuration of your nginx webserver. The server error should look like this:
upstream sent too big header while reading response header from upstream
To solve this problem you should try to add / update your nginx configuration with the following settings:
proxy_buffer_size 128k; proxy_buffers 4 256k; proxy_busy_buffers_size 256k;
fastcgi_buffer_size 128k; fastcgi_buffers 4 256k; fastcgi_busy_buffers_size 256k;
Please check this comment for more details.