Good Morning and Happy 2021~

The lower norgren in the drivers bay is leaking air out of the bottom discharge or vent opening. This valve appears to be serving accessory things like:
Optional kneeling
Door lock
Drivers seat
Air horns
Etc.

I assume that this is a valve failure not a control issue? Anything I need to know before I replace my first one?

Also, since these accessories have their own control, what is the valve doing? Why not just feed all of these things from a manifold? Or is the kneeling option being used as part of the HWH leveling system?

Thanks!