I found the culprit ! I found out that Deco is using the IEEE 1905.1 protocol to broadcast roaming info over the LAN. The new 2.5/10Gb switch labelled Kastenkamer does not support the IEEE 1905.1...

@David-TP Thanks for your swift reply. Herewith the requested screenshots : I also included an overview of my network switches. So yes, there are multiple switches in my network. The majority (green)...

My wifi network used to consist of 8 Deco M5 nodes with wired backhaul in AccessPoint mode. This worked excellent. For performance reasons I upgraded and replaced 3 Deco M5's with 3 Deco BE25's. Same...