Why is the connection reset when saving a post in the Wordpress admin?

Question

Web servers

The problem occurs fundamentally in the Wordpress admin panel (laptop). Other sites work without problems. Internet from MTS, works through a Wifi router.
On mobile devices connected to the same network, there is also no problem. From another computer on another network, the site works fine
. It's worth Kaspersky Internet Security, the firewall turned it off, there are no proxy settings and anonymizers.
Advise, please, possible decisions and the reasons.