Ours did the same thing. Two identical zones wrt square footage, sprinkler head type and count. One mysteriously changed itself from whatever it’d been at to three minutes. See: Reaching The End Of My Patience With Our Rachio 3
I may find myself looking for something different, next season. This controller’s wonkiness has become tiring.
I really wish they’d allow one to turn off much of the “smarts” and provide an option to adjust all zones up/down by a percentage amount. Both of our previous controllers had that feature. It was very handy. With the Rachio 3 I’m obliged to manually adjust all of them, all freakin’ eight of them, individually, as conditions change.