Some site not working properly even with "site without proxy" rule

I am playing around with proxy on NS7.2.1511 (haven’t tried it in previous releases).
I discovered one site not working properly through proxy:
If I acces it through proxy, most time I get “403 forbidden” or default Apache server homepage. It doesn’t matter if site IP is in “Sites without proxy” list or proxy cache enabled/disabled, it is not working through proxy. Other filters are disabled for now, it was a clean installation of NS.
But I can access this site by manual typing “https://” before sitename, I can reach it through proxy.

If I use my another gateway without proxy, it is working as http and https also. Can you try to reach this site using your proxy if there is some issue with site or with my proxy, please?

If I try to open I always get 403 Forbidden, with or without proxy.
Using https, I see a website about coffee.

I am at home now and I am able to reach the site on http and https also from here.

But at work where my testing NS resides, there is no possible to reach this site on http through proxy, only by explicit force to https. But if I bypass the proxy using my other gateway it is reachable without issues…