If you ever turn on a zone from your irrigation controller and a different or multiple zones come on, it's likely a wiring issue. In this case, whoever spliced the multi-strand wire to the valves themselves did the homeowner a disservice by burying the spliced wires in the ground instead of protecting them with a DBY kit (which we did) and digging out a space for a small valve box to house the connections (which we did but I forgot to record it).

Taking these additional measures, time consuming as it is, is a necessity for the long term health of the entire system as taking short cuts and just throwing a little electrical tape on there doesn't protect the wiring from the elements or pests and pretty much guarantees you'll be calling us to make repairs down the road.