No Internet during long fast downloads.

Ive noticed on my last 2 netgear routers, anytime I am downloading a large game patch at almost maximum speed of my internet connection (1Gbps) All my devices connected to my router stops being able to connect to the internet. Only the computer downloading the file still works but only the download and thats it. On the computer that I am downloading the file I cant even brose the web in a web browser even though the file is still downloading fine. Once I hit pause or the download finishes then all of my devices are now able to connect to the internet again. I have tried turnin on QoS and it still does the same thing. 

Anyone every see this? Always happens when its a big download 10GB or bigger where the download stretching past a few minutes. 

Nighthawk AX4300