@eldhie 

Welcome to the community.

Please reach out to the email and I would like to forward your case to the senior engineers.

They will be able to help you check the problem and re-select the signal source if needed.

Thank you very much.

  @TP-Link After your engeeners said in the remote session "they don't know what is going on" I gave up...

  @Momcho 

Thank you for the further update. I have checked with the engineer, he explained after the compared tests during the remote session, everything works expected on the device itself since it prefers to connect the Deco with a better RSSI rate. As for why a shorter distance had a worse RSSI, one of the key factors are the barriers, which made us think the satellite Deco M9 is not in an ideal location, around the corner or behind several concrete walls maybe. So even though the distance is not far away, the barriers in between blocked most of the signal. In this way, we hope you could relocate the satellite M9, put it somewhere in clear sight from Deco M4 if possible.

And the engineer also requested some pictures of the location of Deco units in the email, if possible, I do hope you can give him an update so that he is able to provide a proper solution for you.

  @TP-Link It was explained very clearly to the engineer, including photos of how close the routers were to each other. If you want, we can put it next to each other????

I got two X90 (you know, your most powerful Deco), because when from the support team tells you "I don't know what is going on", you don't trust the product anymore.

Now connection between Decos is really stable. Only that the other devices are unstable and disconnecting. But I will describe all the disappointments from the most expensive Deco in a new topic ;)

But haaay, at least I have a normal speed and signal now, but half the features are missing.... If you want to have a good signal you should pay 600 EUROS for the routers and after that have a monthly subscription.

Time Limit of Parental Control.... Why, what does it cost on TP-Link to pay for it monthly ??? Call time() twice in the firmware?

And yes, these are the same TP-Link that in 5 years have managed to add only 2 IoT brands to their comparability list with IoT devices - TP-Link and Philips Hue (in M9 Plus).
And these people will advertise to me that they will analyze my IoT traffic if I pay them monthly? HILARIOUS!!! I, who pay for all possible Streaming Services and Cloud space that exists, will never trust this service "HomeShield Pro". What is the guarantee that it will not disappear after 1 year?