@Daveomania 

Yours is really horrible compared to mine.

Simultaneous run:

192.168.1.1 = ISP CPE
192.168.0.1 = Deco M9 Plus
Back to back connected.

I don't remember the whole post but did you also completely excluded the wireless part?  

Same issue with the E4

@bsye Thank goodness I saw this thread - I thought it was just me !! I wondered if it was the inbuilt anti-virus software causing processing problems but it makes no difference turned on or off. 

bsye wrote

Same issue with the E4

@jwb I noticed that sometimes I don't have this problem, but it seems totally random. I tried changing everything, even modding my modem/router. I also noticed that if Deco is connected, the built in wi-fi of my router struggles too.

@bsye 

Your isp modem/router wifi i would turn off. No reason to have it on unless there is a good reason. :P

@Radeondutch I have the exact same issue with my M5 and I only bought this last. Video conferencing even when sitting 2 ft from the deco device stalls and takes a while to get back. Only when I'm wired in do I have no issues. It's as though the deco M5 wifi cuts in and out... Any solutions yet?

@Radeondutch My father's phone is not fully compatible with the Deco, so I had to turn on the built-in wi-fi.

It makes no difference, the problem persist.

It doesn't appear as though TP-Link support has been following this issue for a while. 

I'm not sure there will ever be a solution.

I have tried wired as well which seems to be fine, but I bought this mesh system for WiFi. 

I think I will just have to give up and buy a system from a different manufacturer. It's a shame because in the past I haven't had issues with other TP-Link hardware. 

@jwb How I managed to get my Deco M5 network fast and stable. 

I read the posts in this forum and was suffering the same issue. To figure out how bad the issue was I setup a permanent ping from my laptop (ping x.x.x.x -t) to the deco m5 I was connected to (192.168.68.31), the main deco unit (192.168.68.1), the interface of my Sky broadband router (192.168.0.1) and an address on the internet (used Google DNS - 8.8.8.8). 

I was getting ping times to the Deco units of minimum of 10ms and every ten packets or so it would spike to over 100ms. At busy times I was getting ping times on the Deco units of several hundred milliseconds. So I started trying to fix it:

1. First I disabled the antivirus and security software in the deco app. (I was running the Deco units in router mode.) It did not make any noticeable difference. 

2. Next I connected the main Deco to the second Deco with an ethernet cable using the backhaul facility. (The third unit I left connected via the wireless connection.) I could see some improvement in the ping times.

3. Next I downgraded the firmward to version 1.4.2 from this thread by logging in via a web browser (192.168.68.1) and going to advanced, system then updgrade. This did not seem to make a lot of difference. 

4. After that I changed my Deco units from router to Access point mode which seemed to make a big difference but the ping times were still choppy with a spike to over 100ms every ten to twenty packets. 

4. Next I changed the settings on my Sky broadband router and disabled IP v6 on the internal LAN which seemed to make a big difference too. It stopped the spike in peak times every 20-30ms.

5. I also disabled the Sky wifi broadcast (did not seem to make any difference). 

6. Next I went and upgraded the firware to the latest version 1.4.4 from the app on my phone and this made a big difference too with speed plus reliability is excellent and the ping times came down to a reliable 2/3ms.

Result: I now have ping times to the Deco units of 2 or 3 ms with the occassional packet of 20-30ms. Not very often there will be a packet of more than 100ms but it is not very often - I would say that 95-99% of the of the packets are 2 or 3 ms response times. My network now runs a LOT faster with web browsing, etc. video conference is stable and good quality and the network is reliable. Hope that helps!

@jwb 

I will try disabling IPv6 as you have stated.

Where did you find 1.4.4 firmware? I've been looking around for it and don't see anything official for a download. 

I also run in AP mode now hoping it would stop any NAT conflicts between my router and the m5s.

If you can point me to 1.4.4 I will report back after attempting your steps. 

Thanks.