@SGTM It is not working for me.
 

Still waiting an official solution by TP-Link.

But it is clear that they do not care....

  @TP-Link I tried different options and found that enabling IPTV/VLAN -> Bridge -> Select Port on Main Router is now providing Ethernet access via the other Port.

Works great so far (last 10 min). Need to wait to see if it holds up. 

  @RicXXX 

There is a new firmware released in late December that fixes this issue 1.4.0.  However, while it fixes this issue it creates a new issue that may be worse.  Since the firmware can't be rolled back and it was so impacting to me as my wife and I both work from home, I ended up having to buy a new router. So be warned on upgrading firmware.

DECO X55 firmware 1.4.0 - Constantly releasing WAN IP

https://community.tp-link.com/us/home/forum/topic/741422

  @TP-Link 

Unacceptable that if the ISP Router has problems, the Mesh Deco S7 become useless and the local network doesn't work.
The worst thing is that this problem has been reported for 4 YEARS ago, but TP Link hasn't fixed this bug yet.

They don't care about their customers, simple as this.

I'll not buy TP-Link anymore, simple as this.

I just made my 1star review on Amazon.

I'm just sorry that I discovered this bug too late for the free return.

4 years and no fix for a bug like this???!!!!

UNACCEPTABLE

  @Sus_Deco it's really hard to say as the scanner on this thread objects and blocks messages with competitors names. 
 

there is an open source project for the old linksys routers - and a hardware manufacturer that uses that firmware. The hardware has gli in their name

  @Mark-R Hi Mark.  Can I ask which open source you went with?  I moved from TP-Link (waste of time and money) to Orbi for network and ring for camera.  I'm not happy with either cloud/subscription model. I'm keen to look at open source instead.  mozzie4 at gmail dot com  Thanks

  @noizex I agree. I can't work out how anyone in the company thinks this is correct behaviour for a router function. 
 

and the companies lack of response has removed tplink from consideration for any future purchase or recommendations by me. 
 

and that they publish such incorrect descriptions of how their own products actually work - and then ignore active, but 4 years running discussions like this one is incredible (and not in a good way). 
 

I've bitten the bullet and gone open source for my systems as finding non-cloud dependent commercial products seems hard! And I don't fancy throwing money at others just to find issues and a lack of support once it's too late - like I did wi the tplink. 

Well, I just learned about this the tough way, when my fiber went down and my entire home automation and NAS stopped working. I mean, how is this even some decision that was made consciously? I bought this (quite expensive to be honest) solution to not have to put yet another router and benefit from simplicity it brings, but having my LAN torn down when there is internet outage is unacceptable. I'm really surprised I didn't realize this earlier, but this week I had multiple outages and started wondering - how the hell is my local network not available as well? 

  @C0deape I agree - which was why I chose the products in the first place. They perform well (or rather fast!) and are easy to manage, but this one issues is a complete showstopper for anyone with non-cloud dependent home automation! In my case as well as the lightweight stuff like plex, I also have my heating and some lighting depended on a functional wifi network. This behaviour renders TPlink products inconcievable in this context - and the companies lack of awareness and support is a complete deal breaker for me.

sadly, I then feel guilty even trying to sell the devices second hand - making the 5 decos I have worthless :( I so wish we could get some response from the company (mind you - maybe that's part of what the US authorities are complaining about!). I even tried emailing the UK MD and got not even an acknowledgment of the message.

  @Mark-R it is pretty poor, especially as these issues don't immediately present themselves (so cant easily return the kit). With the potential US ban (which will no doubt cascade to elsewhere if it goes through) replacing the kit might be the easiest option. Shame as the kit options tick a lot of boxes for solid build houses (powerline, outdoor, ethernet backhaul)...