The Continental’s rear end is sagging and I’m worried

So I noticed a few weeks ago that my Flying Spur seems to be sitting a bit lower on the left rear corner when it’s parked overnight, and at first I honestly thought it was just the angle of the driveway playing tricks on my eyes, but after measuring the wheel gap on level ground it’s definitely dropped by about an inch on that side. The car still drives okay for the most part, although I feel like it’s not as composed over the expansion joints on the way to the office, and there’s a faint hissing sound that comes from the back whenever I switch off the engine which I’m pretty sure isn’t normal. I’ve been reading up on the common issues with these air suspension systems and it seems like the struts tend to develop micro-leaks around the 70k to 80k km mark, especially with the heat we get here in the summer. I really don’t want to take it to the dealer because I’ve heard some horror stories about the pricing, but at the same time I’m not comfortable letting just any garage poke around under the car given how complex these setups are with all the sensors and the level control module. A colleague who has a similar car mentioned that he found a Reliable Bentley suspension specialist in Dubai who actually took the time to properly diagnose his issue rather than just throwing parts at it, and apparently they had the right equipment to do the full calibration afterwards which gave him peace of mind. I’m thinking of giving them a call this week because this sagging situation is starting to stress me out, especially since I use the car for client meetings and I can’t afford to have it break down unexpectedly. Has anyone here dealt with a similar problem and managed to fix just the leaking seal or did you end up having to replace the entire strut assembly? Also, how long does the whole job typically take because I need to arrange alternative transport while it’s in the shop.