@Sunshine 

Thank you for your time and effort in this. 

They lose WiFi connection. Some come back up, but most don't. I have to restart those and they mostly will come back up after that. It occurres only with the non wired WiFi products. 

But that's mostly temporary because it will drop eventually. 

I recently got a new P1 meter to measure the electricity we're using and it's the hub to the home battery we're getting. And the supplier and I have been busy for 3 weeks now but don't get it connected in any way through WiFi. But it worked fine in the previous situation. 

The topology is:

Deco X50 5G to switch from switch wired to TV, DVD (home entertainment) etc. and from switch also wired to Deco X50 Nr 1. 

From the wired Deco X50 Nr 1 to switch to several wired devices like HVAC controle, solar panels, 

Upstairs wireless Deco X50 Nr 2 wired to switch. From switch wired to PC, printer, scanner etc. 

Upstairs bedroom only wireless Deco X50 Nr 3.

In the garden wireless Deco X50 outdoor wired to Smart TV. 

I'll wait with the guest network en reconnecting everything to this new network in case the information above gives another insight.