@wateringcan - are the sprinkler valves in the system AC or DC powered? I seem to remember this behavior if the valves are DC based. Very simple to replace the solenoids to be AC based.
Also, the Rachio 3 has a 900 MHz radio (to communicate with their wireless flow meter) that I don’t think is legal in NZ (wrong frequency). Get a Gen 2 to be 100% legal - I think there are cellular frequencies that are in use in NZ in this band.
The standard Rachio power supply is only 120 V power supply - not a 120/240 auto-sensing power supply.
There are several Aussie posters that are using Rachio down under.