Packet loss as seen by the monitor

I’ve been seeing some level of packet loss as seen by the pool monitor:

After digging in and getting the CSV and enabling packet logging, I can see that the monitor sends a group of 3 requests on every check. In particular, it is sending the 3 requests when the check fails as below, and I can see the three response packets go back out. What is unclear is whether the monitoring server reports a timeout when all the responses are missing, or whether only a single reponse being missing will trigger the i/o timeout message.

1638567629,"2021-12-03 21:40:29",-0.00511686,1,8.8,,,0,
1638566887,"2021-12-03 21:28:07",0,-5,8.2,10,"San Jose, CA, US",,"i/o timeout"
1638566887,"2021-12-03 21:28:07",0,-5,8.2,,,,"i/o timeout"
1638566138,"2021-12-03 21:15:38",-0.006736632,1,13.9,10,"San Jose, CA, US",0,
1638566138,"2021-12-03 21:15:38",-0.006736632,1,13.9,,,0,


Timeout means all of the responses were missing. For the example you list probes were sent
2021-12-03 21:27:54.781049
2021-12-03 21:27:59.782919
2021-12-03 21:28:04.785328
No responses were seen by the San Jose monitor.

Is this IP part of a Hurricane Electric tunnel? If so, running traceroutes may not help debug the problem.