I currently have 7 x X55 Decos configured in router mode with a main deco connected to my ISP's router creating a double NAT. My contracted internet speed is 500Mbps/500Mbps but when I perform speed...

Thanks @Alexandre. Main network is already 5Ghz only and I have the IoT network enabled. This is happening for both: 5Ghz devices and 2.4 GHz devices. I guess I'll have to live with it.

@Alexandre. Thanks. If I disable Mesh for that device will it respect the preferred device? I understand what you are saying but it's kind of misleading as there is a label in there that says that...

Clients on my network not connecting to preferred Deco. I tried rebooting all the units but still not working.

@SteveBower have you tried disabling Mesh technology for that device?