@MarkRound Same here. Just installed the Deco P9's. WiFi works fine, but no connection to all home automation bridges which are connected to the Switch behind the main Deco (TADO central heating, HUE lights, etc.). What a joke! Just connected my provider's cheap Router (Zyxek T-50) again between the media converter and Deco again... Waste of money, TP-Link should have made this issue more clear before buying the Deco's!

  @jrd101 you are implying that we are all making this up and haven't a clue. I would suggest that this is not the case as TP Link support have work around and know how to resolve the problem. That implies it's real!

how may have experienced the scenario? most who have bothered to find this discussion will have had a reason to go searching for help  - therefore they have had at least some problems/symptoms. There is however a world of difference between symptoms and identifying a root cause. This discussion has gone to a root cause that we have asleed TP-Link to rectify

and BTW - the reason your system worked is that the 2nd deco provided wireless access into your wired network, and the devices you were using already had IP addresses from the DHCP server that was in the deco that then ceased being a router. You most likely would have started to experience problems either introducing new devices, or as DHCP leases expire.

I can only comment on the system I have - but this fault disabled my central heating control (albeit the actual heating worked as it's on a zwave network), I lost most home automation (as the HA controller is hard wired to the main deco) and most of the HA devices are wifi ones. It's not made up 

  @jrd101 what are you implying here? We did not read? Sure everyone knows wired devices to satellites work. That is not the issue. The issue that got everyone riled up is the fact that the main deco goes apesh*t everytime the wan went down. 
 

Not everyone could wire things up to satellites. Or wire the satellites to main. In the first place, the fact that this auto sensing "feature" is there and not advertised is a problem. To add fuel to the fire, they made it mandatory. QoL (for dumbs) should be optional. 

I wonder how many people in this thread have actually encountered the problem vs. just seeing the thread. I ask because I actually had an internet outage recently and had no problems connecting internally between any two devices, whether wired or on wifi, including a NAS, and connecting to a PC with remote desktop. I have two X20s. My topology is modem -> 1st deco -> ethernet hub with a bunch of wired devices + second deco -> 2nd deco. So in other words, all of my wired devices are on a couple of hubs between the first and second deco. Per the OP: "the workaround would be connecting the wired servers to the satellite Deco units, instead of the main one." It's a little unclear how I satisfied that condition, nonetheless things worked fine. <shrug>

@BMorr69

Good idea! Just did that myself.

  @TP-Link 

Just left a review on Amazon. I suggest others do as well.  If it doesn't get TP-links attention at least it will warn others to buy a different brand...

  @TP-Link 

Adding another disappointed user to the list.  I've moved back to my old router in the interim, whilst i wait for a fix and whilst i reconisder my entry into the deco ecosystem :(

  @David-TP is confirmed in that beta version? because the notes from tplink did't say about this new feature.