Half of the local network is having difficulty accessing the Internet. What's the matter?

Question

linux

Good afternoon! There are 30 computers in the netgear r7000 based local network. Loading the router is not more than 35 percent.
Approximately half of windows users experience problems with long loading pages of sites. The Linux computer connected to the location of the problematic windows computer works without problems.
The routes are the same, pings go fast, no packet loss is observed, dns changed both to local and to Google.
The router has been updated after finding a vulnerability in it, and it is also not visible on the Internet to perform an attack on it. This problem appeared with the update.
Who has any thoughts?

Answer 1

If that same part of the users is connected via Wi-Fi, then there is nothing surprising, the home router will not pull a large number of simultaneous connections, despite the declared 1.9Gbps.
It is also worth checking if the channel is free enough

Answer 2

In your network, purely by chance, no one deployed a fake proxy, and does not distribute its parameters to Windows through WPAD? :-)

Answer 3

Set up a caching proxy such as Squid. You can also track traffic and block social networks, for example.