nginx 502 and related issues

Looks like nginx and codeigniter session library are not compatible because nginx have some limitation on session so issues are possible.

Most simple solution is to ask hosting provider to disable nginx or just get another hosting, tested on:

a2_hosting_logo

Another is to disable nginx on server if you have such privileges, some solution:

http://askubuntu.com/questions/470737/how-to-remove-nginx-and-re-activate-apache

or you can try also this:
Increase the proxy buffer sizes inĀ  nginx.conf file. For instance:

proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;

If you can’t figure this out you can send me for test your
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To sanljiljan@geniuscript.com