@dzqz 

If ISP provided you with the router/gateway to which Main Deco is connected, you can switch Deco to Access Point mode. This will substantially offload Main Deco. See Switching a Deco to Access Point (AP) Mode

  @dzqz that's a weird fw version. Mine is 1.6.1 Build 20231227 Rel. 80438 and very stable

  @Bugs22 I'm on 1.6.2 Build 20240308 Rel. 55841. I don't think it's a weird firmware version - I think I've just updated and you haven't.

My advice would be to stay on 1.6.1 until this is fixed. I didn't have this problem on 1.6.1.

And I've tried on Access Point mode and found the same problem occurs.

  @dzqz 

I have exactly the same devices (version-firmware). Like you after the firmware update i experience a lot of disconnections and slow performance. My main deco is in router mode connected with cable to the modem and i have two more nodes also connected with cable (through 1Gbps switch) to the main one and one more connected trough wifi.  There are more than 50 devices connected to the 4 nodes but most of them are lights or smart plugs. All decos during the day work at 90% to 100% CPU and i keep loosing connection to cameras or seeing lag to Netflix. Before the update everything worked fine with the same number of connected devices. I am one step from throwing everything to trash and buying something else.