When you did the test with a different zone, you used same wires from the solenoid to the controller?
Yes, I just moved the wire from the bad zone to a different zone. The solenoid is 150 feet away in a sprinkler box, so I don’t think it’s the wires or the solenoid itself. After removing the wire from the bad zone, that’s also when I noticed that the +24VDC was present, but that it would drop to 0 as soon as I re-connected the wire.