I’ve had this same issue - I think I am closer to figuring at least mine out. Once my rain sensor activates after a rain , I get random messages that says it’s activated. Sometimes minutes apart, sometimes hours. But constantly. Once my sensor dries out and I get the “rain sensor deactivated” message, it all stops. I’m thinking that perhaps every time my network hiccups (which it seems to do a lot!!!), when the Rachio connects and the rain sensor is already activated, it kicks the message out to say what the status is.
I had had so many messages that based on some other experiences from forum members, that I even replaced the rain sensor before the last rain. But the new sensor hasn’t made any difference.
Has any one else experienced this?