Add New Post OK on the LAN / Private Network, but not on the Public / External

I am one of those that maintain blog.thesmstore.com.

It had a previous problem where adding new posts when connected in the public / external connection takes too long to load (or timeouts appear), but loads fast when connected in the LAN.

Solved already by using:
‘define(‘CONCATENATE_SCRIPTS’, false);’

But another problem happened.

After adding new post when connected to public internet, browser shows “ERR EMPTY RESPONSE” (Chrome).

On other browsers, it will tell you that “The page cannot be loaded”

One symptom of the problem is typing the title of the post, then going to the body, it will attempt to save draft automatically.

LAN: Saves automatically with date and time.
Public: Only “Saving Draft” is shown.

To summarize, everything is OK on the LAN Connection, problems appear on the Public / External connection

Any help will be very appreciated, most especially if it solved our problem. Thank you.