@TP-Link 

1. What are the devices that dropped the connection a lot?

Performance slows down. Until I got sometimes timeouts. On all devices

2. when the internet service was disconnected, were they still connected to the Wi-Fi but no internet? Or the Wi-Fi had been disconnected already?

Yes, still connected to the WI-FI but no internet.

3. Would any Deco turn red when the internet dropped out?

No

Performance before optimization

Performance after optimization

Sometimes nothing passes. Problem is quite difficult to reproduce.

In order to solve the problem, restart all decos (3 peices) and do not use the Optimazation functionality.

  @David-TP 

Hi mine also having the similar issue. 

2. when the internet service was disconnected, were they still connected to the Wi-Fi but no internet? Or the Wi-Fi had been disconnected already?

I'm having the same problem, while with the previous firmware, my Samsung phone rarely drops connection/connected to wifi but shows no internet. Usually only my Windows 10 laptop and PC dropped out from Wifi, almost everyday, and need to manually reconnect them back a few times.

I'm connecting it to my smart TV as well and notice the YouTube connection keeps dropping resolution from 720p to 144p after the update for around 2 weeks plus. 

Currently using DECO M4 2-pairs. It seems the connection getting worst after the update, being using this for 1 year and it's getting worst... 

  @TP-Link We have issues where the 2 deco units will disconnect form the main deco and turn red.

The deco system is placed at my fathers and have been working for along time 1,5-2 years.
Now after the firmware update the decos keeps disconnecting from the main deco and wont reconnect. 

Not even a restart will work, we need to fully remove them from the network resset them on the bottom button, and reinstall them. 
When doing so, the problem is gone for like 1 or 2 weeks. 
This is very frustating since the decos has been placed the exact same place the last 2 years and worked like a charm. 
What do we do from here?

  @PascalB , @TP-Link Since updating to 1.5.4 I also have experiences devices loosing connection. Mostly it's my Google Hubs that lose connection since updating. Before the update never lost the connecting. After the update sever times per day where I need to power off the hub to restore the connection. Speedtest using mobile next ot hub gives me full speed (300mbps) so it's not the connection speed. 

  @PascalB : Short update from my side.

My setup is currently very stable. I don't use the "Optimize network" functionality. That was until now were the problems started. So, no problems observed, very stable setup as long as I don't use the "Optimize network" function.

  @TP-Link Could you plz reply on this issue. 
The Decos keep disconnecting from the main deco. 
I found out that if i go and press optimize network they will come back on. 

But just before i press the button an error is displayed that too much traffic is on the channel... But i cant manually do anything about it.
Im seriously about to through them out of the window!



After pressing optimize they work for like 1 month and the same thing happens over and over and over and over again!........