When it comes to ride height, having the car stay at operational height, the sensors and airbags must be fully functional. No leaks from airbags and sensors intact.

The car will always lower itself if not driven for a few days, goes in to sleep mode if you like. It should however raise itself up by just unlocking with the key, the air stored in the reservoir tank will be released into the airbags, returning the car back to normal height. The compressor will kick in once the car is started, to top up the reservoirs. If you drive the car regularly and it still lowers itself or doesnt go up evenly then the airbags or sensors are the problem.

Feel the airbag by hand and see if it's empty (soft), if so then it's leaking and should be replaced. If it is hard even though it's lowered then the sensor is faulty (or loose).

Also, feel the air hose connected to the airbag (the connection point), it could be leaking from there also.

I'll try and take a pic of my sensor so you can compare....just in case.