BMW 530D estate; Air Suspension would intermittently deflate and not re-inflate... and then it would, without any logic, and hold for a few days before randomly deflating again. Completely deflating. Air Springs had been changed within the past 10k miles, so very unlikely to be that... so, must be the compressor - the most expensive part of the system to fail. Thought I was facing a £1,200 bill (at least) from BMW or another specialist, until I started searching the web and thinking this could be something really quite simple and inexpensive to deal with. Turns out I was right - a sticky release solenoid valve, replaced for £25, and everything is back to working normally.
Having worked through this, the idea that the compressor could be blown and need replacing is highly unlikely. Much more likely it's just one small, inexpensive part of the compressor that has failed through wear and tear - as you'll see in this video, the compressor is actually very robust and unlikely to be a complete write-off.
DiagnoseDan's video on the Suspension Compressor was a really helpful starting point to understand things - but even then he was simply replacing the Compressor rather than fixing it:
• Air Springs replaced, ...