Check the spheres
As I said it takes about 10 seconds to take a flex hose off and check the diaphram .Once you are convinced that spheres are OK you can then check the valves operation WITH the engine running.
If the car doesn't go down when the valve position is changed,the spheres are full of oil (blown diaphragm) .If it goes down and up WITH the engine running the valve is OK. As I said,the main problem with the valve occurs when they leak internally and the pressure in the spheres pushes the oil back to the reservoir and the car drops.
You don't get a rock hard ride with blown spheres,the tires and the springs offer a bit of resistance which is what you may be feeling ( i don't know how heavy you are ,but i am 140 kg and a SLS car never goes down when i get in the back if all is OK ).
I have offered you all the info I have and I have lost count of the cars I have serviced with self leveling and full hydro suspension.
it's up to you to take this advice and work with it. Cheers!.