Zigbee (2.4GHz) with what to suppress/absorb/screen between the controller and the coordinator....

Hello,
I have such a system as shown in the picture.
The problem is that the roller shutter controller tends to connect directly to the coordinator.
Because of the distance and the walls, the signal is weak and the connection is not very stable.

On the other hand, when the signal strength drops to such an extent that the controller selects a 2 metre away
strong router then everything works perfectly.

What can I do (maybe pad the box with the controller with something) to weaken the connection to the coordinator by a few LQI?

Thanks in advance for your suggestions [/img].

And the roller shutter controller is not also a router ?

It's just has a lot less power than the Sonoff E

Added after 6 [minutes]:

I used this tutorial and everything works beautifully when connecting to this router. On the other hand, I cannot force it to always be connected to it https://www.zigbee2mqtt.io/advanced/zigbee/02...stability.html#adding-routers-to-your-network

I in the Sonoff Mini ZBMINI changed the antenna to such a stick-on wifi antenna ( I had from a burnt socket with esp8266) . Orginally it is like a bigger smd resistor ( or rather choke ).
After replacing the ZBMINI there is no problem with coverage on the ground floor and it works without any problem as a router for other devices , previously it did not even connect with the coordinator on the ground floor.