Windows 10: Internet is working on WiFi but not on LAN after one update from Windows 10

Hello. First of all, I am a IT Consultant, so asking help here means nothing else worked : .

I have a client with a new PC new like 1 - 1.5 years, not sh or refurbished . Until 2-3 weeks ago it worked without a problem, Windows 10 from the start. The problem begun after one update, the lan connection stopped working properly, you can enter a site, but a very low speed. When I tested on speedtest, the speed goes up to 80-90 mb but when it gets close to finish I get a socket error message.

What I have tried : driver update on the lan card, deleting and reinstalling the lan card, buying a new lan card, reseting from cmd the sockets and services, all I could find on diferent guides or tutorials.

I used a USB WiFi adapter, the internet is working perfect. Why does not work on LAN ? The only thing I have not tried is to connect my laptop in one lan from the router, to exclude the posibility that the lan ports from the router have a problem.

:)