I recently had a problem where I was diagnosing slow/flakey internet performance for my family over the holidays when I wasn't at home.   I went to the help screen on the app and used the 'Health Check' to help isolate the issue.   eero reported that everything was fine.

It turns out that that my ISP had an 'intermittent' issue that caused packets to their main switch to drop 20-50% of the time (but health check reported all was ok).

Could Healthcheck run a deep/continued ping/scan of the setup DNS servers (in this case it was an open DNS server and a google DNS server).   Five consective pings for those DNS servers would have detected the problem from the eero.  

I needed to be onsite, and run some tests from inside the lan to figure out what was going on.

It is interesting to note that two of my cameras reported to me via email monitoring that the cameras (my network)  went 'offline', while eero reported all was well.

I called this into support, but they said everything was operating ok from their viewpoint. Want to log as a feature request.