e55 a go go

I've rear through what I think is everything I could find in forums (here and others) related to this topic, done all the work myself, gone to an MB dealer etc. Here is my story...

• After a couple months of driving I got the "visit workshop" warning on the dash for the airmatic suspension and noticed over time (couple days) the RR would sag low. This progressively got worse to "stop, car too low" warning and I could hear the leak in the RR air spring.
• I purchased 2 rear air springs from an aftermarket vendor (just the air springs, no expansion tanks) and did the repair. All went well and the air springs filled up quick while I supported the rear with jacks and it settled to the correct height. Unfortunately over night the RR would sag low.
• Just to sure there was no coincidence I exchanged the RR air spring and did the job again. No luck, the RR was still losing air over night.
• I started to look elsewhere. I replaced the plastic air line splitter that comes from the front and splits to the LR and RR with OEM new and new OEM fittings and used teflon tape to seal it up. No signs of bubbles there so I checked that off the list.
• I replaced both rear air spring fittings with new OEM parts and teflon tape to seal it up. No signs of bubbles there so I checked that off the list.
• The rubber hoses that went into the air spring I used bolt tightening hose clamps to re-attached the line. I played with rubber hose and couldn't get it to leak so I loosened it up some and was surprised by how much I could get it to leak with such a small adjustment. I tightened it up a lot more as much as I was comfortable with before braking it which was tighter than I originally did. No signs of bubbles so I checked that off the list.
• I only spayed down the hose line at the expansion tanks near the center of the car. No signs of bubbles there.
• I move to the front of the car around the compressor. I didn't suspect my issue was here but as due diligence I checked it over. I replaced all the rubber lines that looked rough and the air compressor filter just because. I also spayed down all the fittings in the valve block and didn't see any bubbles. Finally I remove the air line from the compressor that leads to the valve block and it only let out what little air was in the short line so I don't think air is coming back through the valve block into the compressor and leaking air. I don't suspect my issue is anything forward of the rear air line splitter because my issue is isolated to the RR and anything up front in the lines would drop both rears as I understand it.

So that's everything I've tried and here is where I'm currently at:

• The air springs fill up quickly and the car sits fine.
• I can drive around for an hours time and not get the "visit workshop" light on my dash, but it could still pop up after a 10 minute drive. This is driving around at below 45mph for and hour, above 65mph for an hour, I haven't found a pattern to my driving style but maybe there's more I could do there.
• When I unlock the car or go to position 2 on the ignition I don't hear the compressor running. Once I start the car the compressor will kick on and fill the the RR back to normal.
• I've always left a jack under the RR when parked for safety and to track how fast it leaks. I did notice that if I let the RR get aggressively low (fender to wheel lip height) when I start the car the compressor will not start. Only when I raise the RR above it static height OR if I use the "raise vehicle" button in the car will the compressor finally turn on.
• I took the car to an MB dealer and they couldn't find any leaks in the mechanical system and tired the entire electrical system and found nothing wrong with any of the sensors or wiring, everything acted normal. I honestly can't say if they tires to re calibrate the ride height or clear codes anything of that nature. I would need to follow up with the mechanic again but I think they would.

Questions I have right now:

• Since the issue is isolated to the RR I suppose I could still be leaking air at the expansion connection but it showed no signs of it. Visually the hose end looks to be in good shape and there is no signs of any corrosion (honestly very little signs of rust on anything under the car to indicate it could be bad. Car is in warm weather with no snow). I'm still trying to figure out if I can somehow get the the clip off and clean it up and possibly use sealer too when I put it back on for better piece of mind but my suspicions are low. Thoughts?
• As I mentioned I noticed if I let the RR height get too low the compressor wont start. Is that a normal safety thing to no blow up the bag? I don't think it is. Is it because there is a lot of twist in the sway bar at that point and something is going on with the rear ride height sensor? Can the rear ride height senor fail when parked with the engine off and screw up the leveling process and leak all the air out of the RR? As I mentioned in an electrical test when the car was running it showed no problems but when the car is running that's not when I have my issue.

Thanks for your guys help. I'm a little bit at a wits end here. My next step would be to replace the ride height sensor in the rear but I'm not sure why that would tell it to drop one corner. Then I would replace the the ride height sensor in the LF. My though there being maybe it's telling it to jack the LF up and it gets there by dumping air from the RR. After that I think I would give up and change the suspension completely but I don't want to go that route and invest that much. I don't want to go the route of the Arnott air springs either because of the cost and I think I'd be in the same position since the RR is low only when parked.