@MaxDECOm9plus 

You say you are running these as Access Point mode, do you have them all cabled into a switch?

If you can post a screenshot of what you are seeing and how you are determining the speed that would help

Thanks

@Philbert 

Hi,

My primary deco is connected via cable to my gateway, which also provides a wifi network.

when connected to that network I measure internet speed with my phone and get download speeds well above 400Mbit/s

When connected to the wireless provided by the Deco I get less than 10% of that. (see attached picture from speed meas log....first three on deco wifi, meas 4 and 5 on gateway wifi (before deco)

@TP-Link 

Hi

I bought and installed 3 deco units in March this year.

Just recently (2weeksago) I experienced inability to stream HD movies via Wireless to my Apple TV, so I connected that with cable directly to the gateway (before (or parallell to) the Deco main) which solved that problem. But still the wi-fi is dreadfully slow in comparison...