@TP-Link_Deco The issue is that some devices (like ring video doorbell) don't support all channels (only up to channel 11 in this case), which means once the deco set decides that's the best channel those devices can no longer connect to my network. This is a huge issue!

Here is a great example. I have two Amazon 4K sticks and both always pickup on the same channels yet the Deco M9 stays on the same channel. Even if I leave the Amazon sticks on which they always are and reboot the Decos they will still grab the same channels. I've also had my neighbours router showup within the same group of channels.

Automated "Smart" channel selection is foolish and unprofessinal. 

I'm glad I happened upon this thread. This absolutely sucks. TPLink is picking the absolute worst channel for my 5GHz band. My devices connect for two seconds and then drop. What's the point of buying this router if I have to limit my network to just 2.4GHz? Will just return and change brands.

@TP-Link_Deco I AM SOO DEEPLY frustrated by this device. I was dealing with some real life problems and got one of these mesh systems in a hurry for a friend and I DEEEPLY REGRET it.

I am an IT professional, but I dropped the ball and made a gut purchased based on a review..

Long story short, these devices suck.

1. No standard web interface.

2. No command line/terminal

3. Not EVEN a serial interface

 Just a frustratingly limited APP you have to install on your phone... and then if you have issues you have to spend DAYS trying to describe the issue with support and wait for feedback.

I should have just bought an asus router or something I knew, but they wanted a mesh, and I just didn't have the time then to look into it further (my mother was dying).

Anyways... I have been so frustrated by this experience that not only will I actively avoid any TP products in the future, but for any person that calls on me for advice, I will tell them to avoid TP like the plague.

These things SUUUUUUUUUUUUUUUUUCCCCCCCCCCCCCCKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK

Count me as another that bought this piece of m9 plus junk. I bought three of these things in a kit and have a basement, main and a loft and this system is total junk and unreliable. Constant interference from neighbors cause dropping out. No way to adjust channels. I spent 270 bucks on this junk crap and cannot even sell it. No buyer would want it knowing it is junk. Just throw it away I guess. I'll never buy another tplink product as long as I'm breathing. 27 pages of the same problem here and tplink does nothing about it for years. That is a sorry state for a company to be in and what a piece of crap.

If you haven't bought this abomionation of a mesh router then don't!!! You will just be throwing your money away.

I recently bought the M5 set.

Initially I thought they were great but as I've started to dig in the lack of access is frustrating. 

I'm battling channel overlaps all over and M5 app say "all fine".

Also, looking at the channel Widths they are too high for my environment.

V. disappointing

@Nikeboy1973 Awesome isn't it? 

To make it better @TPLink does nothing about this. I've been searching the forums and this issue goes back several years with nearly every thread suggesting engineering is working on it and should have a fix in a couple of months, next release... Beyond frustrating!

I've recently had all of my 2.4GHz IoT devices become significantly delayed in responding/connecting. Searching for answers from these manufacturers (Logitech Harmony, SONOS, Honeywell, Amazon Firesticks, Ring...) All of their logs point to channel bandwidth issues and recommend switching the channel to less actively used channels. Sadly, can't do it with Deco M9's.

The network optimization says my network is fully optimized. Using other tools and my ISP router's wifi channel scanning, my Deco's pick the most busy channel to use. I am convinced their algorithm to find and use the least active channels is backwards. 

OK, this has become way beyond annoying now.

I'm locked between 2 immovable objects.

My TV provider (BSkyB) uses wifi to connect to subsidiary boxes.

It's choices for channels on 5Ghz Are

36 at 40Mhz, 36 at 20Mhz, or 44 at 40Mhz (don't ask me why)

I noticed that Decos appear to use Channel 40 out of the box.

I then decided to try and see if I rebooted the main deco, if it would pick up the clash...

=>Your network needs optimizing (great)

but after optimization it switches to channel 44 (groan, no better).

Same applies every time, Channel 40 to Channel 44

Jeez! look at the space I have to work with, and thats your optimzed state!?

@TP-Link_Deco 

to add a use case for more user control. Our car connects to our WiFi to download software updates and allow up to control preconditioning from our mobile devices. Cellular signal is poor on our drive so we rely on WiFi. The car being American only operates on channels 1-10 on 2.4ghz. Numerous occasions our mesh will choose channel 11 upwards which means our can can no longer use this mesh network. Please give us control over the WiFi channel. 
Im based in the UK FYI.