It appears I have found the culprit and hopefully fixed the issue here...

Having been fed up with lack of a valid and worthwhile response from support, I swapped the gateway Eero with another one in my network. 

Shortly after, I noticed that only one client device was connected to the eero that was originally the gateway eero even though several other devices are in their same room and in close proximity.   I decided to restart it to see if that would allow more devices to connect (it didn't) and noticed it was extremely warm.

I have read about these devices running warm after the version 7.x firmware installation which potentially causes the processor to throttle itself resulting in frequent device disconnects or timeouts. 

After the restart didn't fix anything, I removed that node from my network, which at the same time resets it to factory defaults.

While it was off the network, everything was stable with no timeouts on any devices.

After an hour I re-added it back to the network as a "new" eero, and devices in that room have been connected ever since without a single disconnect or timeout.  And the eero is definitely not running as hot.

Your mileage may vary, but it may be worth removing eech eero from your network, resetting to factory defaults and re-adding to the network.

Fingers crossed, but the network is stable how.  Will follow up should the network get crappy again.

As of this morning / afternoon my Eero network was still crippled. Hooked up the TP Link XE75's this evening. Put them in the exact same spots as the Eero's. Network is back up and completely stable. In fact, at the back end of the house I was seeing 60(ish) Mbps with the Eero 6+'s (when it was actually working).

Now seeing around 80-85 Mbps. So a decent network speed increase. My wife will be happy to be able to work from home again when she feels like it.

In case it's helpful to anyone else here - I seem to have been able to get the network stable by rebooting my switch.  I have two 6+ and two eero 2nd gen, all wired backhaul through a managed switch (TL-SG1024DE) and all on v7.0.1-64.  (I have one more eero 2nd gen with a wireless backhaul, but I've kept it unplugged since all those started). 

I read in a comment above about the eeros choking on trying to establish the mesh network and particularly loop prevention.  It made me think about IGMP snooping on the switch, so I tried a simple reboot via the switch's management interface - and it seems to have done the trick. 

I was stable for about a week or so, then just this morning we had a little power outage and the network instability was back (same behavior - gateway LED flashes white for ~30seconds, internet drops, but LAN wifi still up).  I left it ~2 hours to see if it recovered (also to get the kids to the bus and whatnot), but no joy.  I then rebooted the switch again, and - fingers crossed - it's been stable since.

That's all.  Good luck out there.

I think I solved my issues. I justed installed another 6+ and things are better. This is one more access point than I thought I needed, as the problem devices always showed good connection. Only a few hours of testing but so far things are much better.

I too am getting the same issues and about ready to give up on eero.

Have had 0 issues for over 2 years using their products up until this new 7 version.  Have 5 eero pro 6 spread out all over including a detached garage.  After the update the wifi connection is completely unstable. I tested pinging the gateway from a few clients and just like other posters , its timing out constantly and also with pings as high as 500ms. 

I tried swapping the gateway out as it was burning hot to the touch. Removed it completely form the network and put in another one. Worked for a bit then same issue. Wired from the gateway I see my full 500 down / 100 up. Anything wifi im seeing as low as .9 down. 

At this rate no clue what the issue is nor do I really care. May try those tplinks you guys mentioned and be done with this horror show. 

I posted to this thread (see above) very shortly after the firmware "upgrade", I thought I'd rectified the problem after doing a rolling restart (by unplugging) of my 6 eeros. Last Monday I changed my ISP (this had been scheduled 6 weeks ago, so not related to the eero issue), and therefore I had to input the new details into my gateway and restart it. Unfortunately, this led to a repeat of the original problem.

I've thrown in the towel and bought some x75 Decos, I cannot rely on hardware, where the firmware can be replaced without the end user having any choice or control. The Decos allow me to choose whether I want to update the firmware, so I can look at their forums for issues before choosing to update.

It's been an expensive week, I can only hope the the eero team learn a lesson from this debacle.

Happy for you guys. Swipe right and get a room. Getting tired of the email spam.

I have the same problem that has been mentioned here. I find it incredible that a prestigious
 company does not care about the situation or give an answer. I wouldn't recommend anyone buy an eero.