I also have the same problem and think it is hardware related to the m9 V2. I see spikes every 10 seconds or so.

I hope someone from TP-Link can react to this problem and give some tips/advice.

OK, so some significant progress.  That I hope might be of use to someone else.

I was using https://www.pingplotter.com/ to chart the pings, it's free for 14 days.  I was doing this ping from a macbook pro connected by WIFI to the Deco mesh.  Now, I stumbled upon this article at one point : https://apple.stackexchange.com/questions/263638/macbook-pro-experiencing-ping-spikes-to-local-router

Which cites how OSX's location services by default effectively does a wifi scan regulalry and frequently, this has a detrimental effect across the network.  I followed the steps in : https://apple.stackexchange.com/a/348574 to disable location services on my mac.  I could go back and log to find the culprit, but I just turned the lot off - I've no real cause for them anyway.  And as soon as I did that, the ping spike every 50s or so disappeared. 

This issue came about as I was noticing this ping spike on other devices, (i.e. Xbox) which lead me to suspect the Deco as that was the common link, but I suspect the disruptive nature of this wifi scan performed by the laptop was the cause of the issue.

I tried enabled fast roaming, but that made the latency issue worse.  So disabled that again.

Hope this helps.

I have discoverd that the problem is in windows 10 probably.

I installed ubunu linux on my laptop and i have no ping spikes or lag with the wifi.

So i ithink there is someting in Windows that is causing this problem. THe question is what.

THere are a lot of people experiencing the problem with the ping spikes and lag but there no solution on the internet that works for me.

So is there anybody who can find out what windows is doing on every 10 seconds or so that is causing the lag?

My macbooks at home do the same with lag spikes but less high, still not what i expect from the product. 
So not sure if its just W10.

HA !.

I lost two days trying to figure out what is going on and i found this topic :P

I also have exactly the same regular spikes :)

Beside that problem i still know that Deco is much better than Orbi and Velop Mesh !

We just need fix TP-Link Team !

Having the same issue with deco M4... 

Freaking random spiking issue occuring every 5/6 seconds, even though the speedtest went good but then the spiking issue persist.

@Jzlim same issue here with deco m9.  My Wi-Fi overall is fantastic, with strong speeds, good signal low latency, etc

However, if I try to use Google stadia to stream games, or steam link, or other apps for wireless game streaming, it is unplayable because of the pink spikes every five or six seconds. If I hardwire streaming device I'm using, the issue is greatly reduced, but still not perfect.  

The last firmware major firmware update that occurred in the summer helped somewhat, but I'm hoping they pay more attention to this issue.  I'm counting the days to the warranty to see if I have to replace this with a new system :/