@cacb That message means there is a device with weak network signal on the network and the router is struggling to fulfill the device's requests, as the device is not correctly responding.

There is a difference between the internet connection and your WiFi. If the internet access is poor, it won't matter what system you link to it. Have you performed speed tests in each part of your...

@patseeb Why are you adding a mesh system to a mesh system?

As Sky can be a pain with changing routers, is there a particular reason you want to change?

Any updates?

@Rioplata if the purple dotted lines are the powerline adaptors, then yes it looks ok from your drawing.