I rebuilt my front valve block a few weeks ago, in an effort to clean the block, as part of a full system flush I did.
Whilst reinstalling the cleaned valve block, I mixed the two connections of the larger solenoids (which are the low pressure return solenoids) up and the car obviously wouldn't go to ride height (one side flew up as the other stayed down). As soon as I switched them back, the car would return to it's normal ride height.

Did I damage the solenoids (or the newly installed o-rings) by putting pressure on the system in a way that it's not designed for, when I mixed up the connections?

Before the rebuild, the car was sagging a little in about a week or so, after the rebuild the car sags to it's lowes ride height in a few days.
I've checked the fluid level, 5 mins after driving and that has remained the same.
As of writing this, I think it might be useful to compare the fluid level 5 minutes after driving it to the fluid level when the car has sagged. When both are the same, I think it indicates that there is air in the system that is being compressed, or isn't it?
During the effort to clean up the system, I also tried to push the fluid out of the strut with the bleeding nipple opened up. I can only do the bleeding of the system on the front left strut as that nipple is not stuck. The others are rusted stuck.

Could there still be air in the system?

I am playing with the ABC controls a lot, to push air out of the system. I occasionally have an ABC Visit workshop, mostly when I drive the car around 150km's in one go, leave it parked and then start the car after a few hours. A restart of the car fixes this. I did notice the front left strut going up a little slower than usual (I think, when you know something might not be working 100% right, you become more sensitive to these things, that might very well be caused by an parking spot that is not entirely flat)
Oh and both ball joints are up for a replacement next weekend, since the rubber shield is broken and the suspension squeaks alot, so I'm not sure how that affects the system.

 

I would remove the valve block again and remove solenoids to check if the o rings are blown out…hopefully this is all that happened! Happy motoring amigo

 

I removed the solenoids and everything looked fine.
The fluid was still rather dirty though, so I've installed a new filter.
I think I should replace my filter again now..