System has been stable for 8+ months until a couple of days ago. I have two deco satellites directly hard wired to the deco base.
 

Cat 6 Hard wired connections to deco units seem ok. However, the connection fails if there is a (gigabit) switch in between the deco unit and the client.  Specifically, it links but the DHCP IP address assignment fails. This is true for cat6 connections to the router as well as the satellites.