@Quest7 

Most older devices use the 2.4 GHz band which can cause issues. The band tends to have the most devices on it. It also gets a lot of interference from non network things. The old devices do not use the latest tech and many do not update their firmware. Moderen routers need to handle the latest tech but also revert to lower tech to handle the older devices. The older devices may be at or beyond the end-of-life cycle. A device on your network may cause issues for other devices on the network. 

A few things to do.

Do use separate SSIDs for each band and show the SSID. If you have a guest network, use it to place the older devices  and IOT devices on it. Look for things that can cause interference and see it it can be the issue. For example your garage door opener may is in the same signal range as you router. Use channels that do not overlap. Use smaller channel widths if connectability is key. A different router may be better or could be worse. Make sure your router's firmware is up to date.  Moving the router or changing the position can make a difference. I turned my router 45 degrees and moved it about 3 feet and that makes a big difference in my coverage because of the placement of a fireplace in relation to the router.  

  @ArcherC8 

So true about 2.4GHz and unreal how many devices still only use this band.  In order to eliminate interference, I spent several days monitoring the Wi-Fi channels and working with neighbors to eliminate interference.  I encouraged my neighbors to use 1, 6 (mine) and 11 and to reduce their channel width to 20Mhz.   I also as far away as I can get from them on the 5GHz band selecting 36 and 149 and dropping my channel width to 40Mhz.  I have one neighbor that wanted to work with me, the other was having no problems so no luck there.  The good news is that for most part even though one is still using auto channel and width settings, the router stays away from me and most of the time low interference, though can get to medium due to their channel width.  As well as locking down channels and narrowing channel width, I have a seperate SSID for each band. I have also confirmed my firmware is up-to-date.

I have thought about moving the router around, but when I initially got it I spent a lot of time testing different positions until I found the sweet spot that resulted in the strongest Wi-Fi signal in all parts of my house.  It may be time to try move around again but what has me confused is that my smart tv that is the farthest from the router and weakes signal streams live tv, movies etc with no problem at all.  My Samsung S21 Ultras also can be anywhere in the house or yard and no problem at all.  It is true these use 5GHz a lot, but they do at times use 2.4GHz and the laptop has been on 5GHz and had issues.  The cameras (CQ1, CQ4, CG5 and CG6) that have the most problems a lot are new and one is a model that just came out.  You will see their indicator light come on... then go off... then come on.... as connection getting there but the device and router struggle to talk. Often you have to do reconnect or the device even crashes and reboots and once back and has new connection, everythig works great.   Once a device hasn't been active for awhile and you try to connect, it can occurr again.   I keep going back to thinking that when a device sits a bit or goes idles, the handshake between the device and router is getting off.  I definetly think when the channel and channel width was changing it amplified the issue as my new x-sense mailbox alert would reset each time, but still do not know what the core reason for these challenges or how to fix it.

  @Quest7 

In my network, it is the Wyze cams that are the most problematic. Most work fine but one of them in the garage seems to always have issues even when I changed to another Wyze camera. I ended up moving the camera to a nearby location. Strange that I have another cameras in the garage father away and do not have issues with them. 

  @ArcherC8 

I ran ping tests against 8.8.8.8 and 192.168.0.1, but unfortunately did not have the router default gateway ping enabled, though I now do.  I was never seeing any packet loss.  Soon I noticed my PC starting to slow down and again ran ping test and discovered 50% to 75% packet loss  (see attached). I noticed a few minutes before it started that the Joined updated which again makes me think there some sore of correlation. It then got really bad and saw disconnect and reconnect. The Joined updated again, and still exact same ping test results. I ran ping test using Wi-Fi Toolkit on phone….. 8.8.8.8 average ping 27ms with 0.00% packet loss… 192.168.0.1 average ping 5ms with 0.00% packet loss.  It kept disconnecting and reconnect and Joined updated but same issue.    

Ran Windows Network Diagnostics and it had to “Reset the "Wireless Network Connection 6" adapter”   After this it appeared to be working again until I ran the Xfinity Speed Test that start off fine and then stop work and got oooops message that it couldn’t complete and then the Wi-Fi disconnected again.   This time I did a manual disconnect and reconnect and the Wi-Fi was finally working and the xfinity speed test ran fine.  I did notice it switched bands to the other 5GHz.  I then placed it back on the other 5GHz band by disconnecting and reconnecting and confirmed that one was not working fine too.

This is consistent with all my devices where they can no longer communicate.  It is usually just one or two devices and not all of them.  They are connected but struggling to communicate often after when I see Joined has updated.   To get to connect you have to reset, reboot, try a disconnect and reconnect, etc.  I did check and I do see some interference, which is currently at a medium, but the thing is once reset/reconnect the device is fine and continues to be fine under same situation and is always isolated to 1 or 2 devices at a time.  It also seems if router was going bad we see across all devices so can't help to wonder if some sort of configuration/setting issue.   My ISP is xfinity... any suggestions?