Could not connect to the internet or even could not connect to the wifi

Recently, there are a few reports from users that they could not access the internet even though the devices connected to wifi.

Some are even failed to connect to the wifi.

Both of the cases waiting for a few minutes or restarting the devices, things might go back to normal. But I wonder why this happens ?

The latest one, happened around 15 minutes ago, I checked the admin console, the Services icon goes yellow but nothing showed.

I checked also the terminal of running processes, I don't see anything special.

I wonder what should I check next time when things happened ?

There are also some high CPU alerts quite periodically on the morning 4am and "firewall goes down" notification from time to time.

Edited TAGs
[edited by: emmosophos at 7:10 PM (GMT -7) on 28 Sep 2021]