I have been having persistent issues with certain wired devices losing internet connection.  My network setup is shown below.  The two PCs with wired only connections on the basement switch will occasionally lose all connection with the internet.  In the past, randomly rebooting everything (the Decos and the switches) and unplugging and replugging all the Ethernet cables has eventually restored their internet connections.  In my last troubleshooting spree, I discovered that unplugging cable Eth_D brought the two basement PCs back.  I had previously unplugged my basement Deco (which I thought might have fixed the problem, but apparentlly didn't) to try and fix the basement PC internet access issue.  I also notice that the Deco app will sometimes tell me that my satellite Decos are using wireless backhaul, even though I have wired connections to all of them.  I suspect that something is detecting a network loop between my wired and wireless networks, which then results in disabled ports.  The Deco app does not appear to have any functions which are of any use in troubleshooting this problem.