@bitla1 Yes, you can connect as your description. When there is an Ethernet cable between the Deco units, Deco will use Ethernet backhaul, if not, it will choose to use the Wi-Fi backhaul.

@Koennl Hi, Sorry to hear that you have some difficulties with the Deco M5. We can do further troubleshooting and try to fix it. What is the current network topology/diagram? And what is the light...

@KoenCrabbe Hi Koen, Normally, the Deco system will recommend the client device to roam to the closest Deco unit when the device is moving around. However, whether to roam or not depends on the...

@Aleksander According to the instruction of the air conditioning, it's supported by Deco M5. Can your other devices work fine with the Deco M5? If so, it's suggested to contact the air conditioning...

@MahanA Have you tried to set up the problematic Deco to be the main Deco? If not, you can have a try. And check if this Deco will work properly when being the main Deco.

@JonCahill You can refer to the link below to swap the Deco M5 to be the main Deco, and then update the firmware via the Deco app. https://www.tp-link.com/support/faq/2400/...