I didn't have your exact problem, but I did have the valves randomly switching between pool/spa mode. It ultimately ended up being a faulty spa side remote switch. It's a Jandy 4 button, and apparently, (according to the tech who came out to replace it under warranty), they are notorioius for failing and randomly sending signals to turn on the spa/heater or whatever else you have the buttons programmed for. Just an avenue to explore, may not be the cause, but it was the cause in my case.