Zone 1 turns on with 28v but all other zones are receiving 19v

I have a Rachio Gen 2 controller. When I went to turn on my system this spring, I noticed that the zone I turned on had weak pressure. Upon a closer look, I saw that other zones were “leaking”. I removed all wires from my controller and tested the voltage of each zone. When I turn on zone 1, it receives 28v however, all other zones are receiving 19v. Keep in mind ALL wires are disconnected from the controller at this point. After 20 mins of troubleshooting with Rachio, they agreed that the unit had failed. So I went online a purchased a used one (yes, I know).

I plugged the new unit in with the power cord it came with, and now that unit is doing the same thing. It was never hooked up to my sprinkler system at all. When no zones are on it shows 0-1 volt.

Do I really have two units that have failed in the exact say way? Is this a common problem with Rachio Gen 2? Is this a setting in the unit that I am overlooking?

Thank you for any and all feedback.