Thank you both for your input. Perhaps I'll try taking the valve apart
and seeing if I find a crud deposit. Otherwise, it's new valves for
me.

I agree with the statement that these valves are pretty crappy. I
bought Orbit valves because they came in a three-valve assembly and
that's just what I needed. I don't think I'll purchase any more Orbit
in my lifetime. Hopefully Rainbird is of a higher quality.

Best regards,

-Fleemo