I actually noticed these outages first when I looked at my Homeseer logs (I had installed the Opensprinkler plugin, which polls the OS for status on a regular basis). While checking my Homeseer logs, I noticed a few “could not communicate with opensprinkler” errors. At this point, I actually disabled the Homeseer plugin, in case it was somehow overloading the OS. This is when I pointed PRTG at the opensprinkler, and started with the pings every 5 minutes. Per my original post, the outages occur about once per day from approx 5 to 30 minutes. I have observed this consistently at some point each day that I had it on my network (from mid March to last Friday). The timing of these events does not appear to have any regular periodicity.
I understand that the OS may respond differently to ping than other requests, and that not replying to a ping may not necessarily mean that the OS is “offline”. However, for me, the acid test is connectivity with my Homeseer installation. My intention was to integrate it into my HA system. For that, I need to be able to communicate with OS 100% of the time. I wish I had more time to play with this, but it’s the start of irrigation season here so I just want something that works.