In the affected network the RV082 was the Internet, DNS and VPN gateway with 2 WANs. The computers were obtaing DHCP leases from RV082 with the RV082 as DNS server. It took quite a time to find it out, but the problem was related to DNS. Depending on the network traffic, RV082 was slowing down to the point of almost complete lock of its WEB UI. The reason was a bad DNS entry. The ISP turned the DNS serwer off. But the RV082 was still using it. Since two DNS servers were specified, everything was working most of the time, as the other DNS server did the job. The slowdown in DNS queries was visible, yet not alarming. I'm assuming, the DNS queries sent to the bad DNS server were consuming the router resources or CPU power in some way. With rising amount of DNS queries router was beggining to slow down, to the point it took a few minutes to open a WEB page.