Hi

I also have the same issue, I have 4x KP105's. Initially it all worked fine then anything connected through wifi were reporting issues of the internet not available. Sky Q Router looked fine was reporting all ok from its point of view, also anything connected via ethernet cable was working fine. After a bunch of tests and reboots I saved the config and did a factory reset of the Sky router, restored the router config and still the problem persisted. Again I did a factory reset of the router but kept the defaults, this worked for a while, but the problem reoccurred.

I couldn't work out why devices could connect to the wifi but not get a connections to the internet but cable devices could using the same sky router. I made a manual change to my mobile phone to enter a manual ip address, gateway and dns address 8.8.8.8, this worked! So I still thought it was something to do with the Sky Router, after another reset and a slight tweak to the DHCP and IP address range it seemed to be stable for a while.

But then the problem re-occurred. I thought back to what I had introduced at the time of the first occurrence because the network had been stable for ages, the only new thing was adding the KP105's. So while there was a problem I switched all of the 4 KP105's off and after a few minutes devices started to work again on the wifi and access the internet.

There has to be a problem with these devices which is causing on the wifi that is flooding or corrupting the DNS, or something similar. I have a large house with 6 people living here and hence there is usually between 30 and 40 devices connected to the network.

I am having a similar issue. My whole network goes down the moment I try to add a Kasa Smart Plug. Been having them for years now but now they started acting up. The moment I configure the smart plug to connect to the network, that network goes down and I cannot connect to it any longer. I have no ideea what is causing this, maybe it was introduced in a new firmare as, like I said, I had these smart plugs for years now and they never caused any issues like this.