Guess what, manually changing my IP address solves the problem. With or without VPN, the problem is always tracked down to the nexus servers. The only reason for this is because the server blacklisted my last IP address. Returning to them make my download slow again, the test show that the requests by my last IP are being denied by the server, local IP address don't change the route, all the devices in my house uses the same router, and only the computer that most uses nexus are with slow download speeds. The server is not doing this purposely, I trust nexus and now that they are honest and fair. This can be happening due to a bug, is what I believe. Since you specialize in internet networks, then it should've been immediately obvious to you that by using a VPN, it routes you to a different location, and thus, uses a different download server from the Nexus than you usually use, probably one that's not as busy as the one you use by default.