I've just get the Deco M9 Plus Mesh Wi-Fi System. I've applied the latest firmware available.
This unit is configured to run as access point and is connected to internet with 1gbps download and 200mb upload link using a fiber gateway router. When I test the speed using the Deco app I get arounf 800mb download 200mb upload (no problem here). When I test the wifi just near the unit with one iphone 7 I get 300mb download and 200mb upload (no problem here I think).
This unit is installed on the living room and when I go to the room no more then 5 meters away with only one wall in the middle I get 30mb download and 12 upload.
What can be causing this? Why is this connection slower then the wifi connection of the fiber gateway? I've just get the M9 to increase the speed and coverage and the connection is worst then before.