I have my deco w7200 set up as a router. One node is using wireless back haul and I have an older w3600 with Ethernet back haul in my basement. I have 500 Mbps fiber so both upload and download speed. It worked great for the first little while I had it. Now it seems to be limiting my upload speed to 75Mbps. Download is still very fast. 

When I plug my computer directly to the modem I get 500 up and down. Also when I restart the decos I get 500 up and down for about 1 to 2 minutes then it goes back to limited 75Mbps upload speed. The download speed is always fast. 

I have Qos disabled but have tried it enabled also. I have tried toggling most of the settings in advanced. I have disabled real time protection and parental controls. 

Any ideas what could be limiting or slowing my upload speed? It helps greatly when I am working remotely.