Sorry this is so late (only 18 mo.) I’m browsing these forums. Who knows if you’ll find this or not…
You’ve replaced and tested with everything that’s involved except the wiring from the controller to the valves.
If you are doing a long run and using telephone wire or some thin stuff, bite the bullet and get some proper #18 AWG sprinkler wire.
Long runs with thin wire will reduce the voltage needed to pull in the solenoid, or once pulled in you may be losing voltage across a bad connection. Did you solder them or use wire nuts? Are the weather protected?
Just a thought.