I have 3 Archer C6 Routers. The main router dials PPPOE to the ISP. The Second and Third Router acts as Access Points and are connected directly to the Main Router using Ethernet.

I can roam seamlessly between the Second and Third Router. However Internet stops working when I roam to the Main Router. I can still ping public IP address but browsing stops. It remains like this for 3 or 4 minutes and then everything works fine.

Another way to make it work is to switch the Wifi off my device and then wait for some time. After turning Wifi back on it connects to the Main router and works fine. 

What could be the issue. Anyone faced this type of problem.