I updated my two eero Pros with 3.18.  I didn't have any issues after the update and all my devices were able to connect to the internet.  I'm running ping for 24hrs to see if the issue still happens.  I'm not that hopeful given eero support told me there was a good possibility that something was wrong, but they couldn't start to troubleshoot it until I had Comcast fix my occasional internet connectivity issue.  But perhaps they miraculously fixed a related bug which was causing our connectivity issues...  one can dream!  :)

3.18 update for me has been nothing but trouble.  My eero network (pre 3.18) has been stable for months, and along comes this steaming pile of garbage. 

After a reboot, things initially seem good, then blammo! every 10 minutes or so I encounter about a 20 second network outage.  Very upsetting.  Since the update, the LED light on the gateway stays solid white, indicating all is well, but my lack of connectivity (both WiFi and hard-wired) says otherwise. 

Tonight, however, I noticed a couple of occurrences of the gateway having flashing white light, so I decided to switch the units around and make a different node the gateway.  Of course it did not help, after no more than 10 minutes or so there was that dreaded 20 seconds of network outage (solid white light).  So I got to go through the whole 'delete network' and recreate it from scratch rig-a-marole for zero benefit. 

Tomorrow I'll go and dig out the Orbi's I have in the closet and see if their firmware has gotten better since I got eero, because eero's firmware has definitely gotten worse.

I would like to add my 2 cents into this thread as well.  I have a 7 eero system made up of all original A010001 units.  Five of these eeros are hardwired and 2 are wireless.  I have been using this setup for at least 3 years now and had come to rely on it.  However, since the recent updates I also notice many similar issues to what people are posting in this thread.  I also use comcast.  I also updated my modem recently because of the disconnects.  Currently, I am using a SB8200 modem with 600/15 service. The random disconnects have not stopped but seem to be less with the 3.18 update. 

What is really bothering me is a specific issue with port forwarding.  I have a number of forwards setup, nothing crazy just 4 forwards to a workstation that I leave on all the time.  I connect to this system from work on a regular basis via a couple of services that I have the ports forwarded to this system.  The port forwarding on the eeros is not working for more than 48 hours since these updates (I am not sure which update, specifically, but it started with the new user interface on IOS).

The only way that I can get the forwards to start to work is to reboot the eeros.  This is where the disaster happens every time.  It used to be that I could run the software reboot of the system and a minute or two later all the eeros were back online.  That is definitely NOT the case anymore. 

It is rare that the software reboot is actually successful to reboot all the eeros and get them back in a working mesh. What usually happens is that a few of them come online and the rest sit idle with red light indicators on them.  The really frustrating thing is that they kind of appear to work if they are wired, but if any wifi device tries to connect, it just fails.  This has been a total disaster with 7 of these and how random it is. 

I have tried removing various eeros and adding them back, but nothing really seems to help other than going to every eero and manually pulling the power cables out of each one and waiting 10-15 minutes.  After this waiting period I plug the main eero connected to the cable modem in and subsequently add each eero manually one-by-one assuring it is able to mesh.  This process takes me about one hour each time and is obviously not acceptable.  

I am at a loss for how to solve this issue.  I need my port forwarding to work, but I can not perform this manual reboot every 3 days. 

I am having the exact same issue. This has happened with the last four updates and has bricked two satellite repeaters. NOT HAPPY.