Seems to be a common problem Eero can't fix.  I have given up trying to deal with support and just live with the constant disconnects.

Briefly, I have had problems with internet stability since 6.0.4. I keep having to unplug my modem and gateway to reset back to normal. This fix works for a day or two and then it returns. This problem never existed prior to 6.0.4. I'm suspicious...

Same story for me. I upgraded to the PRO 6 hoping it would stop the "dropouts" - and they are still here. I have a 1500 sq foot house with the pro6 as the main, a PRO as a beacon, and a second beacon. The EERO support team's suggestion...move the additional beacons further away. I can't...it's a 1500 sq foot house.  Piss poor support for an expensive router, with ZERO real solutions, when clearly it's a common problem with their device. 

Ever since the last eero firmware update, various devices like Nest Protects, Wemo light switches, and plugs, etc. are dropped off the network. The only way to get them back on is to reset the network. Never had this issue before the last firmware update. How can I go back to the previous one? Anyone else seeing this? PC Drivers

Honestly as of this point I feel that eero should do the responsible thing and roll back the update - very irresponsible decision on your part. While all the responses here and in blogs through out the web are pleading for this to be resolved all eero can respond with is to call. So then we call and wait, and wait, and wait - unbelievable. I, along with many, desperately need this resolved considering work remotely and am constantly having to use my cell phone to connect for meetings. Further more we are having to deal with connection issues preventing us from being able to do our jobs efficiently. 

At this point I think I am going to leverage my skills, as a targeted campaign guru, to position eero in such a way that they will have to either fix the problem promptly or refund me for my investment in them. I believe this is where the beauty of the internet and social media can represent those of us that are being subjected to their poor decision making.

Same issue here that seems to have started before I upgraded to 6.5.1 (though I see 6.6.0 has been recently "pushed" to me: no release notes so assuming early release from Eero for troubleshooting purposes?).  I feel like the issue is about 3 weeks old though could have been longer and I only pinpointed once I started trying to track the occasional "your Internet connection is unstable" notices from my web conference tools.

I tracked by running continuous ping (2 second interval) from multiple systems in my home and all experienced timeout at the same moment. Also at that moment, all Internet traffic was disrupted. I've swapped the Gateway Eero with others in the house so that each of the three has now been the Gateway at some point.

I've tried blocking all but the most essential devices from connecting (note that I've not added anything new so everything on my network has been on my network for over a year).

I've replaced the Eero with my 10 year old 802.11n router and the problem goes away.

I've connected directly to my cable modem with one computer and ran the same ping test and the problem goes away (tested for 16 hours straight).

I've dropped to a single active Eero and the problem persists.

I've connected to Ethernet on the single active Eero and the problem persists (though other items were still connected via wi-fi).

Here's what I see (RELIABLE_DESTINATION=whatever you want to ping that you expect reliably responds all the time):

548 fails Sun Nov 21 07:02:07 EST 2021 64 bytes from RELIABLE_DESTINATION: icmp_seq=25169 ttl=53 time=191.986 ms
548 fails Sun Nov 21 07:02:09 EST 2021 64 bytes from RELIABLE_DESTINATION: icmp_seq=25170 ttl=53 time=241.700 ms
548 fails Sun Nov 21 07:02:13 EST 2021 Request timeout for icmp_seq 25171
549 fails Sun Nov 21 07:02:15 EST 2021 Request timeout for icmp_seq 25172
550 fails Sun Nov 21 07:02:17 EST 2021 Request timeout for icmp_seq 25173
551 fails Sun Nov 21 07:02:17 EST 2021 64 bytes from RELIABLE_DESTINATION: icmp_seq=25174 ttl=53 time=51.782 ms
551 fails Sun Nov 21 07:02:19 EST 2021 64 bytes from RELIABLE_DESTINATION: icmp_seq=25175 ttl=53 time=125.526 ms

I'm tracking above using this bash command:

i=0; ping -i 2 -A RELIABLE_DESTINATION | while read pong; do echo "$i fails $(date) $pong"; [[ "$pong" == *"timeout"* ]] && let "i++"; done;

…so I'm counting both timeouts (551) and total attempts (25175 @ 2 second intervals). Above is after I rebooted all Eeros because it had progressed to 10-15 seconds down every 2-3 minutes. You see from above counts that's about 13 hrs and usual drop is about 3-5 timeouts so 551 ÷ 3(5) = 110-183 drop "sessions" over 13 hrs is about 1 "session" every 3-4 minutes.

I am told to expect replacement units. I think they are only wanting to replace two of the three so we'll see what, if anything, changes.

I started having issues with signal dropping a couple weeks but only on my laptop computer. Fire Stick, android phone, and Samsung tablet had no issues. I thought it might be anti virus and VPN settings. Switched anti virus and VPN software. Still had issue with signal dropping.

Figured out an apparent solution today. It appears the signal drop is browser specific and I'm not sure why. If I reboot my laptop and open Firefox the signal will keep dropping. If use Chrome the signal is stable. If I open Chrome and then Firefox, the Firefox browser wifi signal is stable. Not sure why there is an issue with Firefox????