Hi all, i'm planning to use this thread to post my particular issue and how i fixed it in case it can help anyone else as i didn't find a huge amount on the issue when i started looking.

I have a (new to me) 2009 RRS L320. Everything seems to be wrong with it but the main issue has been a suspension fault that told me to stay below 30MPH and it wouldn't change down from off road height. Having reset codes and the like i could get the front to lower, but not the back, then they would both go up.
Anyways, the error message i was getting was C1A13 (C1A13-64 to be precise) 'Pressure does not decrease when venting gallery'. It seems this is about the system working fine to increase pressure, but then can't dump it to drop back to normal/lower heights. At this stage, I suspect some element of the exhaust is blocked so will try to get the compressor off (will post a separate question on that) and then report back here what the problem is....to be continued

That does sound like the exhaust valve in the compressor (or some part of the tubing from it) is blocked/failed. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Ok, final update on this one...eventually got the bracket off and the old compressor out. Put a cheap (£75 from Amazon) replacement one in while i try to rebuild the original. A £2 collet in the male hex quick connect stud wouldn't hold so i was getting the C1A20 - Pressure Increase Too Slow When Filling Reservoir.

Pulled that compressor out and put in a third one (this time £70 from Amazon but doesn't look as well built as the £75 one) which is holding fine and no more (suspension!) errors.

As this is the first time i've ever seen LR / RRS suspension work, not sure if it's working correctly - seems very stiff, creaky and uneven to inflate (and even deflate). Is there any quick trick to making it smoother (and therefore probably faster)?

Try it with the car in neutral and the handbrake off … the increase / decrease in suspension height slightly changes the wheelbase length for some scientific reason that I cannot fathom on a Sunday evening

Funny enough, I noticed that exact same thing.... Is a bit smoother when it has 'room to move'... But was still clunky.

If you're telling me that's normal then all the better. Else keen to know what to spray/squirt, and where, to make it a bit less clunky.

The bushes on a 2009 are going to be a bit worn by now so some creaking isn't unexpected. As for uneven rise, I think that's a classic "they all do that, sir".  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed