That was sort of what I was thinking but since I have not played with it in several months I could not think of a reasonable way that the connection would be lost but that was just a possible guess. Your response sort of supports that thought.
The lost connection idea does bother me since the rest of the data is fine, that would make one assume that the system does not think that a rain sensor system is attached. But you would think the design would not monitor that just report no rain. A missing sensor you would think would default to a “nil” or zero value.