@BobMuk 

I have the same problem

Hi jacktiew - I just looked at your previous posts, it looks like you only started getting this issue since 1.4.2 firmware came along, is that correct? I'm asking because if that's true then at least it's something that can be fixed (if it got broken they should be able to rectify) rather than being something specific to my network that can't be fixed.

@TP-Link_Deco are you the support team?

I would attempt to run in router mode (and remove the Archer A7) to see if that fixes it, but I've got a bunch of DHCP reservations that I'd need to move over and don't have the hours available to migrate them to the Deco.  Is there some tool for importing the settings from an A7 to a Deco?

The reason I'm a bit suspicious of the Archer is that I used to have a C7 and some TP-Link powerline adapters... I'd get the exact same symptom that I'm seeing now when the powerlines were running (drop-offs) - the fix was (for reasons unknown) to disable NAT-Boost in the C7.

However now I have the A7 (though pretty similar to the C7) which already has NAT-Boost disabled, and I don't have the powerlines any more - but

Looks like this is my last shot before returning the Decos to Amazon and going with another vendor - I just don't have the time to mess about with something that's supposed to "just work".

@TP-Link_Deco 

Hi -

1) Obviously when I posted originally this FW wasn't available so I was on the previous release.

2) The units were working on ethernet backhaul, and every time that I checked that this had not changed (when the issue was occurring) it the app reported ethernet signal source.  Given that the issue was also evident on devices connected to the main Deco, and indeed devices wired (via a switch) to the main deco then I don't think this was relevant.

3) So this is what fixed it.  I went through the effort of migrating my settings (port forwards, DHCP reservations) to the Deco and switched into Router Mode, removing the Archer A7 - and the network has been solid for a week.

So there's some incompatability between the Archer A7 and the Deco M4 (while in AP mode).  Note that all of my networking kit - my 2 switches - is TP Link, as was the Archer A7.

Did TP Link ever test this configuration? 

I get that it's not possible to test your kit with every brand and model of router that's available in the field, but surely you tested with your own routers?

@TP-Link_Deco 

Mine is using Xiaomi. I'm facing same problem in AP mode. I was on router mode for testing purposes previously. No problem for two day, and then after switching back to AP mode, the problem come again. 

@BobMuk Hi, did you manage to resolve the issue?

I just bought M4 set today, similar setup (AP mode, Ethernet backhaul, 1gbps lan, 1gbps downlink/150mbps uplink, units randomly connected to switches within other infrastructure). I achieve reasonable WiFi speeds (500-600mbps download, 150mbps upload) but I also observe that speed drops after some time to e.g. ~30mbps and then randomly raises again. This is annoying e.g. when watching 4k video.

What I found out so far is that on Samsung mobile the issue occurs only when WiFi power saving mode is on - switching it off keeps full speed. This is however inconvenient:

1) never had this issue with the main router (huawei) before, no speed drop even with power saving on

2) there are devices that encounter the same lag (e.g. amazon firetv stick) however there is no option to control wifi power saving

JFYI - my units are on FW 1.5.2 Build 20210916

UPDATE: Even with power saving switched off on Samsung mobile it occurs time to time. I just need to disconnect and reconnect.

Anybody managed to find root cause and resolve the issue? Last 2 days for me to return the set and consider something else...