@Marvin_S Thank you Marvin. One of the Ethernet ports of the main Deco node is connected to the ISP router Ethernet port. Another Ethernet port of the main Deco node is connected to the TP link...

My three X75 Deco nodes work perfectly well in AP mode with no Ethernet backhaul. The network becomes unstable the moment they are connected to a TP Link switch SG-1016D. I presume this switch is...