@David-TP 

Hello David, so I have tried both wifi and an ethernet cable but neither of the two fixed the issue. The speed on my computer is 45mbps up and down, same as the package ive chosen from the isp. as for the isp wireless router, they have provided a small white box which has a yellow wire with a pon connector connected to it, and ive connected the main deco to that via ethernet, and the remaining two deco are set up in mesh via the app. could you please explain to me the different between WIFI-Router mode and Access Point mode? i dont have any other routers, just the optical network unit from the isp which is connected to the router.