Keep the zone off for a while. If the dripping/leak stops after a few minutes or in some case with large zones, hours, than that is just low head drainage. You'll also notice a lot of "air" sizzling out of the heads every time you turn the zone on, because the water needs to fill the pipe again and take over the air space. This is common when a certain head, and the pipe are at lower/higher levels then others. This is normal for most systems, but can be stopped with a sprinkler head that has a "check valve". A check valve will keep water from leaking out at lower elevations.
If the water is coming out all the time 24/7, then it has to be the valve (debris). The valve is the only thing that stops the water flow. The sprinkler heads do not....if water is leaking out, the valve is the culprit.
If it is the valve, and you decide to take it apart again, then let the mainline flush out before you re install the internals. Did you replace the valve internals, or the entire valve and body?
They're may be some fine grit or sand in the line.
Off topic: Are you on well water or city water?
I'm no expert..........YET!
I just like to suggest things and learn...
See what the pro's have to say first.