@scorp508 I've worked on several spray heads recently that had the blue cobra connector on them. The ones that would not come up were crimped.
When you are closing the "spray adjuster" on yours it builds pressure inside the head and the turret extends. When you open it, the pressure is relieved and the turret lowers back into the rotor body. I think there is a crimp or blockage before the head. It's also possible for a tree root to compress the line.
Regarding the top rubber cap: They will come off, but doesn't go back on very easy, if at all. And I don't think they are meant to be replaced. I've never replaced one anyway.
Dirt is certainly a problem in the adjustment holes on older heads or ones that retract down into the dirt. You may try flushing the holes with a stream of water from a spray bottle to clean them out. But remember, if the heads are low already, they will get dirt in them again.