@pdeseymour Sorry for the delay in responding.  My network comprises 4xM5 and an M4.  An M5 is the master and has 500MB broadband from my ISP.  Three M5s are connected via Ethernet, 1xM5 and the M4 are using WiFi for back-haul.

Standing next to the Master M5, download speeds are as follows:

2.4gb only - 345Mb

5 gb only - 333Mb

Directly connected with PC - 339Mb

So, it looks as though it's not just WiFi that is "losing" speed.  As you can see, somewhere within the Master M5, I am losing around 32% of my download speed.

I hope this clarifies.

David

@pdeseymour This is going from bad to worse.  I now have only 150mb when standing beside the Master.  I have rebooted the D5 and the Openreach fibre termination box and the incoming broadband still shows 504mb.

I'm getting close to going back to my old router!

David

UPDATE:

I decided to go back to basics and factory reset the whole network.  Here's what I found:

1 ) Having reset the Master, I carried out a speed test with no other Decos or devices connected.  Via WiFi, standing next t the Master I achieved the full 500mb!!

2) I continued to set up the next 4 (3xM5 and 1xM4).  I returned to the Master and conducted another adjacent speed test.  I could only achieve some 200mb

3) I then went to one of the hard-wired remotes and conducted more speed tests.  Each time, the initial spike hit 300mb but during the tests, the speed rapidly dropped to around 100mb before stabilizing.

Following the initial post, I was assured of help from tp-link but have heard nothing.  Could you please look into this asap?

Thanks

@pdeseymour Over two weeks ago, I provided the required information but have still heard nothing.  I now have a situation where the wi-fi at all of the five stations drops to 50mb.  This has to be resolved by rebooting the Master and is necessary every few days.  Could I please get some assistance!!!   

@TP-Link_Deco Hi,  I'll address your points:

1) you are correct in your summary.  AS requested, the topology is as follows:

2) I have enabled and disabled the Advanced feature but they had no effect.

3) As shown previously, when only the Master is running, there is very little spped lost over wifi when the mobile is adjacent to the Master.  AS other Decos are connected there is a gradual loss from the master but the total loss in percentage terms when all decos are connected is around 20%he Mobile was adjacent to the Master (Hall).  The mobile device was connected to the Master(Hall).

4) The Decos were purchased on 2nd September.

Please note that the fundamental issue is why the Master suddenly drops to 50mb on Ethernet or wifi (when the ISP feed remains at 500Mb) and the drop is reflected to all stations in the mesh.  This does not seem to be anything to do with which Decos are connected or their position.  The system can remain stable for days before the sudden drop and it is the rebooting of the Master that restores speed to the full mesh.

I hope this provides the information you require. 

@pdeseymour Deco team,

It took some time to provide the information you requested but I have heard nothing.

David

@pdeseymour  Still no response.  I am rapidly losing confidence in this product and reporting progress. It shouldn't be up to "the luck of the draw" in a forum to get technical support.

@TP-Link Hi, on average, I have 13 wired connections and around 20 on WiFi.

I no not have another Router.

Thanks