Hello Team,
Sorry, I am very late here to reply but I fixed my problem by making changes with in the nginx.conf file. It was a very easy fix and was related with the nginx.conf ( And I was trying to fix the core code 
).
I removed this line from my nginx.conf
proxy_set_header X-Sendfile-Type X-Accel-Redirect;
That was fix to make the downloading work 
I will try to be frequent from now on
Thank you,
Ashish P.