Leave router off for 10 minutes in case heat is an issue with it. This also ensures a reboot of it which can't hurt.
Plug ethernet cable into a different port on it.
to analyze packets and perhaps you could pick up on something or gain clues.
Anohter test attempt is to open services.msc
(from start menu search, hit enter.) Disable IP Helper Service and DNS Client service. Reboot.
From command prompt, netstat -an
and netstat -ano
commands for clues (try variation/combination of switches - leave out a, n or o.)