Try disabeling Circle and/or App Armour and the issue will go away.
Now both of these was the reason I bought the Orbi in the first place, but I prefer to have a working network over the ability to contol the kids.
Debugging didn't provide enough information for me to figure out exactly why there was issues with Circle and App Armour, but it could have had something to do with the cpu usage on the router (I could see CPU spikes around the time when the router went into internet lockdown).
When testing, I tried factory resets only enabling either circle or app armor, and both made the router go into lockdown. For some reason, Circle did this faster and more often than just App armour.
I gave up on both Circle and App armour and have a fairly stable network now. I've had issues like network drops happinging only twice the last 6 month, so there are still some issues with the Netgear software also.
I know it's related to the netgear software, because my old Asus AC68U is not having any issues with the fibre network at all (I put them both up connected to the fibe to check for network disruptions and only the Orbi got them for some reasons).
Lastly, the "Test" button also fixed my issues when they happened, these were my observations when the issue happened:
When not pressing the test button, the internet part of the router was blocked for 2-10 minutes before coming back up. When just waiting, the router kept the public IP.
When the "Test" button was pressed, the internet blocking was off after a few seconds and the router came up with a new public ip, meaning that the router probably just refreshed DHCP to test conectivity. I'm also guessing that services like Circle and App Armor restarted when they discovered an IP change and in that way, the internet connectivity was fixed.
