When auto-registration of the active zabbix agent is enabled and the proxy server cannot resolve the host by its ip address (there is no ptr record in the dns server), then as a result we get a host that starts being monitored using an empty dns interface. And naturally we get a server that is not monitored.
Moreover, this host in the zabix was already monitored and everything was fine, but for some reason auto-registration worked for it and updated the interface.

And that added interface, with empty dns, can't be removed: remove button is not active (see screenshot)