I purchased the Deco X20 as it advertised 1200Mbps on 5Ghz.

I have a 1Gb fibre connection. The main Deco unit is in Router mode with a Cat6 flylead linking directly to the ISP ONT. When running the speedtest off the Deco app it shows a speeds of around 900Mbps which is acceptable. 

However when doing speed tests over WiFi the fastest speed I can produce when standing right next to the main Deco is 450Mbps. This is using an i7 laptop with 8Gb RAM on 5ghz (Wi-Fi 5) and a Samsung S10+ (Wi-Fi 6)

I specifically purchased the X20 amd not the M9+ as the X20 offered Gb wifi speeds on 5Ghz and the M9+ only offered 867Mbps.

I am not expecting full 900Mbps over Wifi but 450Mbps is too low. Can someone please advise if the unit is faulty, or if I have incorrect settings, or this is to be expected?