3004.388.8_2-gnuton1 AI-Mesh-Overview lying to me

[Miedelsbacher]

Hey out there, happy new year!

Situation:
I've got a home with approx 200qm over three floors.
Internet coming in via glassfiber (600/200) on the first floor (hillside location, first floor / cellar: walls of concrete, rest of the house built with wood and plasterboard to keep it short), FritzBox 4060 (WiFi deactivated, DHCP-Server and a few devices with fixed IP defined in Fritz!Box). My PC connected directly to the Fritz!Box.
5 XT8 in AP-Modus, first via 2.5G LAN to Fritz!Box, all others via WLan (5GHz, standard-config with 5GHz 2 as backhaul), no Guest-WiFi activated. DSL-Speedtest normally shows 80-100 in the "worst" place of the building.
I have 3004.388.8_2-gnuton1 on all XT8s. Before I updated with original FW until the latest.

The problem persists on EVERY Firmware:

NORMALLY, the AI-Mesh looks like that:

All XT8 connected, Good or Perfect connection. Around 44 Clients connected over all floors.

Minutes after that, it can be, that one, two or all nodes (besides the "master") are not reachable and are marked as disconnected:

Also the count of connected devices will decrease, somtimes to zero. This changes minutes after that back to perfect condition and the process begins again...

But I do not think, that this is really true... Without connecting the clients to the master-node (which is nearly impossible over 2 floors) it is no problem for my PC to reach for example a WiFi-connected Printer in the upper floor. Or other things (weather-station, other printer, lights, switches etc.) in the other floors. I swear, they are not connected to the master in the view of the UI. Fritz!Box Network continues to show all the clients. All XT8 show white steady light.
OK. SOMETIMES some devices are not reachable in such a moment. But mostly the network is still reported as stable by the kids (the real power-users...)

I had this behaviour with original firmware and now it continues with the merlin. Same behaviour in iOS-App as on WebUI

I tried (in my opinion) everything: Use 2.5 GHz as preferred backhaul (nothin changes, Only 5GHz is used). Unhide second 5 GHz WiFi, Reached for other networks in range and adapted the frequency of 2.4 GHz and 5GHz to free channels. Set up everything from the scratch after changing to merlin.

Any ideas?

Thanks in advance

Uwe

yes. From Germany. Sorry for that and my experiments with this language.