I've been dealing with an issue for several weeks (months maybe) where I'll notice that my WiFi connections stop passing traffic. They are still connected to the WiFi network, but no traffic seems to pass. If I try to connect a new device to the WiFi network, it will fail. When I look at the details for the mesh APs, it shows that they have no LAN IP (when operational it displays an IP address as expected). It will also show that the mesh APs have good/great connections back to the main router, and a mesh test will provide similar results. The only fix is to restart the APs. I have 3 total APs, one main router with a wired connection, 2 mesh APs only connected via wireless. I have to restart the APs a couple of times per week.
I have tried moving the mesh APs all around to see if that makes a difference, but since the wireless connection looks good, I don't think that is the issue. It seems like more of an issue with DHCP and the ability of the main router to assign IPs. I have 30+ devices connected (Windows/Android/iOS/Other).
I also recently performed a factory reset on all 3, hoping that would resolve it, but the behavior continues.
I also recently enabled IPv6 to see if that makes a difference for those devices that support it, not clear at this time if this made a difference.
If you are using the first point as a router, try turning off DHCP on the 1st mesh point and plug the cable from WAN port into the LAN port. This forces your main router (not mesh) to give out addresses and making your 1st pt into an access point instead of a NAT router. I have not done this with mesh myself, but with other wifi routers.
I haven't tried that suggestion yet, because the mesh system has been stable since I enabled IPv6. I haven't had any issues with the mesh connections dropping, clients unable to connect, nor having to reboot the devices because traffic wasn't passing. Whenever I've checked, all systems look good and connections are "great".
I'm going to keep tracking for a while, but so far big improvement. Normally I would have needed to reboot at least once by now.