On Nginx, images 30k+ sometimes load

and sometimes load only 10-30 percent...

i am on nginx v 4.13*, with these configs:

has anyone experienced this?

*yes, i must upgrade, though ubuntu's apt-get packages have not updated
for the longest time, and i dont want to risk screwing up my server
configs (i'm a linux newb)... if you have a blog somewhere to upgrade
safely, please share..

thanks a lot!