@EricBoy In Access Point mode, your setup should be working. I have similar setup to yours and it works just fine: Router <----------------> Switch <--> Deco Master | \---- <--> Deco Slave #1...

@DMUM The only thing I would recommend is start fresh. Remove all Decos from your home network in Deco app, and after you did that also reset them manually as described in this document: How can I...

@DMUM In your network diagram I see Main Deco not connected by Ethernet cable to the router. Is this correct, or is this just a typo? Main Deco must always be connected by Ethernet cable to the...

@cstmgl If you have devices connected to main router, it makes sense to switch Deco mesh to Access Point mode. In that mode, main router manages the whole network, Deco mesh only provides WiFi...

@DMUM Consider removing Satellite M9 and M3W from Deco mesh, in Deco app, so that you only have Main Deco M9 left. Then, change it to AP mode. I remember when I set up my Deco mesh, I started with...

@Roy-B On second thought, can you run one more test? Power off edge node in home office room, and from that room run speedtest with mobile device that is now connected by WiFi to one of two remaining...