Air Suspesion Problem

Happy Christmas to all.

When I park my Disco 2 nine times out of ten it will sink to the stops on the off side. If i raise the rear suspension before leaving the car then the suspension will stay up which makes me think its not the bag. Has anyone got any ideas?

The bags can leak in certain parts so at one level it will leak but at another it wont. Herad of this before although not personally experienced it when I had my D2

Compressors are prone to failure but again I have no real experience of those items, could it be a valve that is leaking when NOT under so much pressure? as the issue seems to go away when more pressure is involved.