@AnotherMJB 

Just an update.

I have not observed the network stability issues that other have reported. However one of my M5 mesh networks is at my cabin in a remote area of Vermont that has no cell coverage, no neighboring WiFi (the nearest neighbor is more than a mile away), and the network is old fashion DSL over copper telephone lines. There are only three devices on the network as no one is up at the cabin, nor has anyone been up for about a month. Just a printer and a smart APC UPS, both plugged into M5's via ethernet cable (not WiFi). The only "wireless" device is a sensor. Yet after about a week, if I ask (via the app on my cell phone 150 miles away) the TP-Link app to do a Network Optimization on that mesh network, it will report the network as being congested. Seriously? One wireless device on the entire network, the other two devices connected to M5's via ethernet cable. And no cellular or neighbor WiFi interference? And it's "congested"?

After I tell it to "optimize" the network, if I ask it check again, it reports everything as "perfect". But after about a week, this isolated mesh with 3 devices (only one on WiFi) will report as "congested" again.

So it's puzzling as to what this function actually does or how it analyzes the mesh network.

@AnotherMJB  I have been in contact with Support and pressured them, through a manager, to retrieve details on the new "features."  I shared the link to this conversation and she has promised to exert as much pressure as she can to get some answers from the development team.  She said she will respond on this thread if she receives the requested documentation.

@AnotherMJB Not only is there no documentation, my network is now non-optimized. My 3 Deco M3s are now using 2.4GHz channel 3. This channel is not recommended for use, as documented in FAQ for TP-Link EAP product network optimization: https://www.tp-link.com/us/support/faq/2511/

" We recommend to use channel 1,6,11 when deploying 2.4GHz network (with 20MHz Channel Width). "

So how can a 2.4GHz Channel 3 assignment be optimal for a Deco network?

@edp Running the 1.4.9 20200924 Firmware, my Decos have chosen Channel 2 for 2.4Ghz. In this firmware build, there is no way to choose the channel... It seems to be working with no connectivity issues...

@navigator48 Do you have that article about downgrading? I'm having trouble with Wemo's on  1.5.1.

UPDATE: Found it https://www.tp-link.com/us/support/faq/2958/

UPDATE 2: I did not downgrade yet but I did disable beamforming as per another post, and it seems to have made my network more stable. Waiting for my devices to show back up in the Wemo app.

UPDATE 3: All Wemos show up, no packet loss, full connectivity ... I think beamforming is FUBAR in the latest release (Deco M5 1.5.1 20201022 Rel. 66804) with certain devices.

@coolspot18 My experience disabling Beam Forming is consistent with what your describe. With Beam Forming enabled, I also experienced the packet loss issues with the 1.4.9 firmware as well as the 1.5.1 firmware.

At this point running 1.4.9 firmware with Beam Forming disabled, my network is completely stable with the exception that sometimes streaming YouTubeTv via the Amazon fireTV 4k stick, there are hiccups in the cloud DVR playback. I have reserved the IP address for the fireTV stick, also enabled, "High Priority". It has full bars connecting via 5G to the Deco. Last night I changed my network DHCP settings to use 1.1.1.1 as the primary DNS server, and 8.8.8.8 as the secondary DNS server instead of the default Comcast DNS servers. Will see today/tonight if that improves playback. From what I have read, 1.1.1.1 is the fastest publically available DNS server available.

@AnotherMJB   Hello, everyone!  I contacted support and requested documentation on the new features.  After reaching out to their development team, they were not able to provide quality details and there is no documentation.  This is the information I received.

The new Network Optimization lets your Deco intelligently scan for a clearer channel and switch your devices to it, guaranteeing optimal WiFi performance.

The ignore ping from WAN feature can avoid the Deco be pinged by others using the WAN IP address, which improved the security.  ’Ignore Ping from WAN’ is for network security. It just avoids to the WAN attacks from others.  The Deco will ignore the ping from someone else. And it will not send back data pack to someone else. It can save equipment resources in this way.

I had two questions:
1.    Are there any possible negative effects to enabling “Ignore Ping”?  For example, could this cause a disconnect by my internet provider, Alexa devices or from active websites in my browser?
2.    What does the “Network Optimization” feature do?  

Responses were:

Ignore WAN ping has no negative effects, and it just ignore the connecting from someone else who we do not know. And it won’t block ISP network and other client devices. Alexa devices or from active websites in your browser are working ‘inside of your network’. All of them are connecting the deco’s wifi, so they won’t be blocked. But the WAN ping is from outside connecting which is at risk. For security issue and better performance, the deco will ignore the WAN ping from outside. And it won’t influence your network.

For the Ignore Ping from WAN, please open Deco App, then go to More > Advanced > IPV4.

Network Optimization is because deco ignore the WAN ping and it will not response someone else’s connecting. In this way, the deco will save some ability and make the network more stable.For the Ignore Ping from WAN, please open Deco App, then go to More > Advanced > IPV4.

To contact Support for additional questions or troubleshooting, please use this email address (support.usa@tp-link.com) and share helpful details in this post!  I fortunately am not having stability issues right now and I did enable "ignore ping."  

@AnotherMJB I just got my network set up and ran the optimization. It said congested and the said perfect.  I immran it again, same result. So I'm not sure it is actually doing anything!

@Jimboreeno Why can't they just allow us to select our own channels? That's basic router settings. 

@AnotherMJB  I started getting serious drop out issues on my Sonos System wich is operating on its own Mesh network (Sonosnet) by connecting a Sonos Boost to the Deco Router, it establishes it's own network.  Anyway, thank you for all the sleuthing and feedback on this forum.  I disabled beamforming, reserved IP address for all my devices and then optimized the network (which was also showing congested).   All fine now with current firmware.   I've also got WiFi Calling on my Cell phone and was getting horrible reception.  I think this will fix it.....   Thanks to all of you.