Bought a triple set of Deco's M5 last year, after my TP Link Archer didn't cover the house enought.
Put the Deco's in AP mode and connected them hardwired to the modem/router from my ISP. Everything worked fine on different UTP port on the modem.
I got a new setup-box from my ISP/TV provider (same company). With it came a new modem.
When i installed the new modem and setupbox my internet went down. After trouble shooting for some time, i noticed that when i removed the second slave AP deco, internet worked fine.
Even put in a network switch to devide the UTP connection between the mediabox, AP Deco and the TV. Nothing worked.
It only worked when i disconnected the Slave AP Deco from the UTP, it then would use the wireless backhaul from the main deco and work. But that slowed the internet connection down.
Als tried to connect the deco with a new cable directly to the modem/router. After a couple of minutes it would kill al network/internet traffic. Even wired traffic at a different port.
Removed the slave ap deco from my main deco and reinstalled it twice. And one time give it a reset. Same problem, no internet.
What could this be? I now need some extra coverage in my house and would like to use the second or thirth deco!
According to the first topic in this map, in AP mode all deco's can be directly wired to the Modem/Router.