Problem accessing the site through a router?

Question

Domain Name System

Good afternoon.
There is a site, I send a lot of requests to it via a wifi router (not as many as in DDoS) to the site. After a while, the site stops responding, but switching the cable straight without wifi, everything works without problems.
The router was replaced, the problem remained. (There was a Dir-300, it became zyxel keenetic).
DNS was replaced with Google's 8.8.8.8, the problem remained. During the problem, nslookup ip determines, but the site still does not load.
Reinstalling the firmware on the router revives the site for a while and then again, even a reset does not help.
What could be the problem? Thank you.

Answer 1

some kind of mysterious Wi-Fi killer site .. a lot of requests - how much?
per request - socket?