@David-TP In fact, I have two wifi routers. One is TPLink X20 and the other is th one that ISP provided. If my phone joins X20's network, I can see that TV. Once my phone switches to the other WiFi,...

I had questioned about the security for X20. And I also submitted other for this but no solution. https://community.tp-link.com/en/home/forum/topic/516494 Whatever, I reset my 3 decos to be MESH. And...

@David-TP Thank for your reply. It's difficult to set 'deco' mode as the layout of my environment is not good for it. My house is 4 floors and the deco in each room is hardly to be connected due to...

@Alexandre. Thank you for your reply. Here is my comment: 1. Neither kids nor the teenager are existed in the house. 2. Guest network is disabled from the beginning. Never will be enabled. 3. As my...

One more, All devices such as phone/tablet/desktop/laptop etc are under my control. It's not possible to have device connected which is mine but I don't know.

@Alexandre. Thank for your reply. Here are my responses: 1. Guest mode is disabled. 2. I had chaned password once and still see others. Then I asked your help. 3. Now all deco are working on AP mode,...