@ah1stb 

I finally got my network stable. See if this works for you. Set up your main DECO and WAN and leave it as wireless BEFORE you add any LAN nodes. Add your LAN back slowly until your whole LAN is back online. Then add the deco's back to the LAN one at a time by plugging them into the LAN until all are back online. 
 

Alternately, you can try to add your main deco and LAN, before adding any satellite decos.

What was happening to me was I tried to add the satellites back to the LAN before the network was stable and completely reattached. I had unplugged my LAN nodes and tried to add them back in a sequence. The wireless nodes were connected to the WAN and portions of the LAN simultaneously and they were competing with the main deco in supplying internet to the LAN. Once the main deco saw the competing signal, it shut down the LAN ports.

hope this works

  @TP-Link 

I also have same issue with my deco x20

My CCTV decoder always disconnect 
Before I use deco x20 there no issue my cctv disconnect 

Same issue here with Deco E4 v1.

Went mad after a few power outages caused chaos with home network.

After a complete reset, I had things up and running for a sustained period only to find devices would randomly drop connection or be unable to connect at all. I'd have a device with wired connection working just fine but wireless device would not be able to connect and wired connection to main unit broke everything. 

I was forced to switch from router mode to AP mode for my own sanity and have now had a constant network for 24 hours. BUT if I dare to connect a device as wired to the main unit, internet connection is dropped for all devices. 
 

Then I came across this topic and learned that some design decision is behind this! 

Deco E4 v1 hasn't seen any firmware updates since 2021 - is there something planned?

  @TP-Link 

Same Problem here with 3x PX50, 1x X50-Outdoor and 1x X50. After adding the X50 via LAN it worked awesome for ONE DAY and in the evening, there's not even one LAN connection made anymore and everything tries to connect via WiFi. This is bonkers.

Firmwares:

PX50's: 1.2.1

X50-Outdoor: 1.2.4

X50: 1.3.1

It is such a disgrace. The 3x PX50 worked together perfectly, and we felt so lucky to finally have a great powerline solution. The added X50 broke everything.

Currently, we still have 1 week left on Amazon to return everything… I'm pretty sure, that has to be our “WORKAROUND” to this mess.

  @bcamp4390 

Thank you so much for your solution - it helped me get my LAN back (weird statement...)!

Can confirm my implementation of @bcamp4390 worked for me:

1. Make sure that in the DECO app >>> More >>> Advanced >>> Operation Mode is set to “Wi-Fi Router” and your WAN-router is in bridge mode.
2. Shut all DECOs down = unplug all power cables, keep the LAN/Ethernet cables connected! If PoE: Unplug related Ethernet cable. The WAN-Router can stay active/online.
3. Power on/plug in the main DECO unit with its “WAN in” Ethernet cable (from your router in bridge mode) attached and wait until the green LED is steady and shows an Internet/WAN connection in the DECO app. While starting up, it may be confusing (at least for me), that DECO units tend to start up (the steady yellow/light greenish LED) and switch directly to the red blinking LED (= no connection) but turning into a steady green LED (= connected) shortly afterward, so be a bit patient. At this moment, the auto-sensing should've set the WAN/LAN choice on the main DECO to WAN and everything else to LAN. DO NOT SWITCH OR MOVE THIS SINGLE ATTACHED ETHERNET CABLE.
4. Power on/plug in the first network element with an Ethernet cable connected to the main DECO unit. Network element means: If you have a network switch or LAN endpoints/computers that directly connect via Ethernet cable to the main DECO unit, it would be best to plug this in first, before any DECO satellite units - At least, that was my experience. Seems like normal endpoints don't fool around that much, as they don't have the extensive router/mesh/blabla stuff going on. They just want their IP via DHCP and get an internet connection from the main DECO unit, and can't fool around with WAN routing capabilities. If your first LAN attached device is a DECO satelite, power it on/plug it in with its Ethernet cable attached and wait for the green LED (see 3 above). PoE devices would be the last ones.
5. Repeat step 4 until every LAN device is connected, then power on/plug in Powerline/PLC connected devices as some (PX50) directly make use Wi-Fi repeating/extending and have extensive routing and WAN/LAN auto-sensing capabilities.
6. Power on/Plug in the rest of DECO Wi-Fi only satellites slow and steady, always wait for the steady green LED before turning on the next one.

Additional Note: I activated "WAN Unicasting" when accessing the main LAN IP set in the DECO app (for example: 192.168.1.1) via browser and navigating to Advanced >>> System >>> System Parameters 

@TP-Link 

I think this underlying problem is also the cause for multiple threads throughout different forums on the internet where people ask how to set a different signal source! They wonder why that DECO satellite/router connects to the wrong DECO satellite/router because the LAN connection is missing and what's left are the Wi-Fi and powerline signals! That was also my case: I stumbled across this thread only with little hope and before searching and reading a lot about (no proper available) signal source selection, as I was just seeing that my DECO satellites did connect via weak powerline or wi-fi signals far away, although they were connected directly via ethernet cable to the main DECO unit.

  @ETANET 

Your description is a logical way to recover a system - the issue is that it should not fail with the internet is removed - and so you should not be put to this inconvenience!

and it doesn't matter if its a router or an access point - the Deco products all misbehave in the same way when their access to a cloud service is removed. That is completely unaccaptable!

and mine had the recent firmware update self apply yesterday - at which point they wiped the 'guest' network settings and changed them to someting I have never used! this is also garbage behaviour.

unfortunately I've had my devices too long before finding these issues out - so I cannot return them, other wise I would!

  @TP-Link Welp, glad I found this post. I'm returning my X55 system because this exact issue happened today after my internet blipped. I Couldn't get it to connect, tried troubleshooting for awhile and finally I unplugged the cable from the ONT into a different port and it worked. This was after multiple restarts of the system. Ridiculous. Going with ASUS XD5 since I've always had good luck with them, not to mention the customization and FREE features, unlike TP Link. I don't think this system has been updated with the so called "Fix" as stated on page 350,000 of this thread.