Is the crack on the side of the ball valve handle? If it is then it's because it's a ball valve. As your turning the ball, the opening inside allows the water to hit the crack, as it's fully turned on- the ball opening isnt touching anymore.
I see this happen all the time.
Sounds to me that what ever zone that the heads weren't popping up has a broken pipe and or broken sprinkler head.. Walk around the zone and look for a break
It is on the back of the ball valve so you are right about that.
I am waiting on the replacement to take care of that issue.
As for the broken pipe or heads, all my zones act the same. It appears that I lost considerable line pressure.
I have the well guy coming over to investigate as I believe the water pressure dropped everywhere including the house.
I will update after his visit.
thanks,
R