I Have a pack of 2 of deco M4R units, wifi was setup, apparently no issues. The network topology is

WAN - ISP router (bridge port) - deco M4 (1Gbps+ cables all over, all ports are 1Gb).

I have exactly the same setup I had with a tp-link wr1043nd v3, that I have now replaced by the pack of 2 deco M4R.

Just bought 3 new nokia 2.2 (android one 9.0), and already on their setup+updates I noticed that they would drop the connection in the middle and I had to disable/enable the network to keep going with the setup!

Now, to definetely troubleshoot this I reset the decos, created a new fresh network with only one deco (left the other unconfigured and powered off), changed the dns of the WAN to 8.8.8.8 + 8.8.4.4, and disabled fast roaming. Nothing else. My tests are being done within 3 meters of the deco and the ISP router.

I also reset 1 of the nokia 2.2, besides adding the google account, nothing else was changed.

I also enabled the wifi on the ISP router (that I keep off) just for testing and comparison. 

I am using the android youtube app for tests, I choose a fullhd or 4k video of more than 20 mins and just play it and see if it goes through all of it.

On the ISP router (I selected my own channel 6 here): no issues, connection always fine, speed fine, video plays all.

On the deco (apparently selected channel 9): issues, deco shows white led all time, other devices seem fine, but these nokia 2.2 the wifi shows connected, apparently no issues, but anything net related does not work (sometimes it will show "connected/no internet"). A disconnect + connect works again for some minutes (around 5-7 mins).

I already tried everything on tplink foruns, even spoke to nokia support to see if they had any wifi compalints (had none), checked nokia 2.2 reviews (also no wifi issues). I also notice that on some samsung tablets, using wifi 2.4 the speed is bad (at 1m from the deco!), starts fine at 50+Mbps but drops fast, eventually the average is listed at 5Mbps? With the older wr1043nd, also 1m away, I had the max wifi speed (120Mbps!), and I also get max using the ISP router.

Testing a laptop PC or samsung tablet on 5.2GHz wifi on deco I also get the max speed.

I also noticed by peeking at the http://192.168.68.1 (default) that the CPU keeps going up to almost 100% for nothing, then returns to decent 4%, this keeps going in a loop, does not look normal... I do not see anything major on the logs, the deco shows nokia 2.2 connected, nokia 2.2 shows wifi connected, but there is no internet at all!

I also changed the nokia 2.2 to use a fixed IP instead of dhcp for the deco wifi, I stil have the same wifi conencted/no internet issue, tryed disable mesh for this device, still issues. Nothing seems to fix it. This would need a good debug on the deco unit ...

This is very annoying, and I need to keep doing disable/enable of the deco network to have stuff working. Connected to the ISP router wifi, no manual changes and no issues whatsoever.

I think there is something wrong with this firmware for the deco M4, that causes severe issues within the 2.4Ghz wifi, causing "some" client disconnections, and I cannot troubleshoot further, if this is not fixed, since the nokias work fine woth other non-deco wifi's, I will have to return the decos since 3 devices at home cannot use it?

Just reset both decos and swapped the roles (always keep only the main on) and the issue is still there, turn on wifi, start a youtube video, after 6:10 it shows buffering issues and I try to open any link, shows disconnected (but wifi shows on, and the deco also shows nokia 2.2 connected).