I have a similar issue with my first zone as well. I believe that the sprinkler valve solenoid is at fault. When the system shows that the zone is running, but it actually isn’t watering. The current usage shown at the bottom of the page on OS is very high, usually something in the 457mA range. When the sprinkler is actually working and actively watering the current usage is in the range of about 240mA.
I haven’t had time to troubleshoot it yet, but I’m pretty sure that is my problem. The valve is a 30+ year old Champion brass valve so the parts are kind of expensive, but once I get it working again it will likely outlive me before it has another issue.