Thank you both for your helpful replies! It makes sense that the level-control valve necessarily checks backflow from the struts and accumulators, and this certainly seems the most likely source of symptoms my 560SEL is exhibiting.
But...
I'm not seeing how excess
forward flow is "checked". At what point in the system circuit is desired pressurized hydraulic fluid in the struts and accumulators prevented from simply bleeding out toward the reservoir bottle in the normal forward direction? After the accumulators, does the circuit somehow route back to the control valve again to accomplish this regulation? Or is some other mechanism involved? (Clearly there's some way this is accomplished back there, since the reservoir canister up front is not pressurized.)
Thanks again for clarifying how all of this works.