I have 3 Deco X20's in my house, and one of them is always causing trouble.  It often gets a red led (offline) and has to be restarted, and other times it says it is online and ok, but has no devices connected to it.

I have tried removing it and re-adding it to my network, I have tried connecting it both wirelessly and via ethernet backbone.  Any suggestions on how I can troubleshoot this device and why clients often will not connect to it.

It is in the middle of the house and is the closest AP for many devices.