I am a proud owner of the 3-pack Deco M9 Plus, which I just setup in my house less than 2 days ago.
I updated most WiFi devices (now 17 and still counting) around the house to connect to the Deco, and all have worked superbly. No more blackspots everywhere I checked too. And no connections dropped so far, as far as I am aware.
In addition to the WiFi devices, I do have a couple of computers as well as a NAS at home that are connected via LAN, where I used to connect my old d-link router to a switch (fairly old tp-link 8-port 10/100Mbps switch) for that purpose. When I connected the 2nd LAN port from the main Deco unit to the switch, everything worked fine as well.... until yesterday evening when I realized that the connected devices no longer have internet connection. The Deco status light is still green (on all 3 units), and all WiFi devices connected to the Deco still work fine.
I tried looking within the Deco app to see if there is any reported status of the LAN port, or whether there is an option for me to disable and reenable the LAN port, but could not find anything.
Wonder what may be wrong.
I plan to, but have not tried the following:
1) Restart the main Deco unit.
2) Connect my wired devices to one of the Satellite Deco units (I am using wireless backhaul, so both satellite units have both LAN ports available).
Any other things I should try?