Here’s the OS setup I had for the “short test”. Both OS units are connected to TP-LINK TL-WR702N for Wi-Fi and Tripp Lite TLP606 power strips for power (both were recommended for OS, IIRC). I had rebooted the remote station OS so that I had both the remote station icon, SD icon, and network connectivity icons displayed. The master OS was still in the state where the SD icon was not displayed, but I had network connectivity.
I then used the OS app on my phone (over Wi-Fi) to attempt to run one of the zones controlled by the remote station for a short duration (15 seconds or so), which normally would have been enough time to actually see the sprinklers start up and water. They didn’t water (which was explained by Ray’s aforementioned post). I then (from the same physical location where I have good reception for the master’s Wi-Fi) started a zone controlled by the master for a similar length of time and those sprinklers watered. This replicated the problem I had the previous time with the remote station not watering. I then rebooted the master and repeated the test. This time both the remote station and the master zones watered.
The power sag/interruption wasn’t very long, maybe 2-3 brief sags over the course of maybe 5-10 seconds. I don’t remember how it was the first time I had this problem.