Network problems. Where to look for the reason?

Question

System administration

At office we observe very strange problems with a network.
There is a server (the problem is specifically when connecting to this server) on the Internet, we access it via HTTP\HTTPS, with some frequency - for 2-3 minutes the packets completely stop reaching it. At the same time - this only appears when trying to connect from Windows machines, while everyone on the vend has no access - everything works without interruption on Apple (Mac) devices.
At the same time, new ssh connections also do not work from Windows machines, although the already established ones continue to work without problems.
Where to look for the reason?

Answer 1

Well, purely as an option - make sure that there are no machines on the network with the same IP addresses.
It is just very similar to the fact that several machines share IP and packets go either to one MAC address or to another.

Answer 2

option 2. crooked hands and / or incorrectly configured gateway. to choose from

Answer 3

It is visible to be infected with a trojan or just torrents creating 100500 connections that your gateway starts blocking.