Land Rover Repair: Land Rover Disco 2 1999 air suspension, intermittent fault, hieght

Question
Hi I have purchased a Disco 11 with air suspension
somes time it works normal as it should then for no reson at when i park the car the suspention wil drop to the bump stops then rise when i start the car
another time the suspension will not rise at all and then after travelling around or coming back to the car later the suspension will go with out any further problems
but i think the best one is i will driving along the highway supention has been graet for miles and it will just then drop to the bump stops and will not raise evan if i stop let it rest or do any thing it will not go up

i dont think the bags are leaking as 2 thirds of the time the car will sit in the garage or acar park after a trip and the suspension will not drop
and i can also raise it to max hieght when all working ok

Any ideas  

Answer
This is an intermittent fault, unfortunately had to find without proper diagnostic tools (Rovacom, Autologic etc.)

It could be leaky bags, as they will leak sometimes and not others.  When its at normal height look at the bottom of the bag, if it's cracking/dry-rot looking it's time to replace them.