I have had 3 Deco X20 units set up and working fine for months but in the last week on 2 occassions the 2nd ethernet port on my main unit has seemed to stop working. I have the setup as per the image below where the modem connects to my main deco and then to a switch which is connected to a number of things including my 2 other Deco units.

All of the things I have connected over ethernet stop working at once, so the backhaul on both other Deco units fail and are too far away to reliably keep using wifi to connect, smart heating and lighting controls go down access to my NAS is down and the network ports throughout my house are not usable. I have tried connecting directly to the unit rather than using the switch to see if that was the where the issue was but get no connection and have swapped out the cat 6 cable from the Deco to the switch and confirmed that was not the issue so the source seems to be the Deco's 2nd Ethernet port.

I have seen some people post similar issues but only mention the ethernet backhaul not working, but with all ethernet connections going down as a result of the issue it is causing me a lot of problems, is there a solution or something I am missing and why has this only happened now after months of working without issue.