Setup:

- 2 bedroom apartment with solid walls across each room. In-wall ethernet wiring for each room. Living room has main router. 

- Deco X75 Pro is the main router with User/Pwd PPPoE connection to cable provider

- TP Link TL-SG105 5 port gigabit switch connects Deco X75 main router to in-wall wiring connection points

- One each Deco X75 in each of the bedrooms connected by Ethernet backhaul as confirmed by deco app

- All Cat 6/6e cables

Switched from old Orbi RBR50 mesh as I got a new 1Gbps fibre connection. 

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Screen mirroring stutters

Living room TV connects to Office router over living room - office router is on the other side of the solid wall while living room router is 10m away.

IF I turn off Office deco, it connects to bedroom router which is two solid walls away - about 20m to 3om away. 

IF I force it to connect to the living room Deco, then Wifi on TV shows disabled and I can't connect. 

When phone is on living room deco and TV on office deco, screen mirroring stutters while smooth on the playing device. 

I managed to force TV to living room deco for short period, and no stuttering. But after I rebooted the TV, the WiFi shows disabled even when the other two mesh decos were shut. 

Create a guest network with only 5Ghz and added both TV and Phone, no stuttering. TV was on office deco, and Phone was on living room deco. 

Currently mesh is all configured to allow 2.4Ghz and 5Ghz. 

How do I resolve the stuttering issue without having to switch to a guest network everytime I want to screen mirror?

Thansk in advance