I had 5 zones stop working last week without any zone detection faults being registered in the log. I finally began to investigate when things starting looking very dry...
What I found was:
* Output voltages looked good at the controller - 27-28V.
* One zone valve that I checked was only receiving 19-20V AC
* After probing around I determined that my common line feeding the 5 zones must have a bad connection, but was not completely broken.
Fortunately, I had another nearby common line (this is a 200ft run so really lucky) to wire to, that fixed everything.
So my question/comment is "Why didn't the Rachio detect this problem ?". There should be a way to set an alarm for low valve current on a valve by valve basis to find this kind of thing.