From what I've gathered after reading many, many posts, I would start with checking all of the suspect wiring harnesses. You've already indicated the oil level wire was bad. I would check all the harness for insulation failure first. I'm about ready to acquire a 95 SL600 and that will be my first project, rewiring the harnesses.
My car is a 91MY with CIS KE-Jetronic fuel injection, so it is exempt from the wire harness issue that affected the 93-95 LH fuel injection cars. The wire of the oil level switch I mentioned was a bit brittle yes but just the end connecting to the oil level sender, due to age and extreme heat here.
I'm suspecting the ride height solenoid that Pazo mentioned in his post and I pm'd him as well regarding that. I didn't have free time yet to tackle this issue, but most probably I will in the next week or so.
Now everything works fine with the exception of the ride height switch. After some high speed testing
I can confirm that the sport/comfort button works. The car has way less body roll when sport mode is activated, and is a bit forgiving when comfort is selected.
The only thing that is a tiny bit disappointing is the level of comfort with ADS isn't what people claim or made it up to be. Then again, I probably had very high expectations. I've been watching a lot of those old Citroen videos to get a better understanding of how the system works, but most probably the Citroen older cars have a much different iteration of the system that is geared more towards comfort. Some of those cars can drive on three wheels
I'm quite happy with the sport side of it but the comfort side isn't as comfortable as my 1996 E320 W210. That car has 16 inch tires though and I have the staggered 18 inch AMG setup. So that probably explains it.