I was asked by David-TP to create a new thread and to answer some questions regarding the specifics of my particular Deco setup;

How are the Deco units connected?

They are connected via WiFi Backhaul

Are the problems similar to those listed in case 3 of the Fix unstable connection document?

Unless I'm missing something, the devices that drop off line are not mobile devices. They are fixed in location. They seem to get reported offline when they are inactive, like an outdoor video camera or thermostat.

Did the Ethernet connected devices have a similar issue?

If the Ethernet connected devices are on, then they seem to always report as connected. I've not seen one showing offline while they are running.

For the most part, although many WiFi devices show offline in the Deco app, when those devices are queried, or need to report something, they connect and have complete network access. If there's a delay, I don't notice it. It seems as though the last firmware update? has reduced the device delays. I really don't know. I stopped looking at the offline devices.