rear suspension issues

Hi, I have an 01' Discovery II. Recently my passenger rear suspension drops every time I hit a bump to hard, or take a turn to sharp. I've tried the soapy water test on all the connections I could see without any success in finding a leak. If it doesnt deflate by one of the reasons stated above it will remain at normal height, so I don't think it's the bag, but then again I seem to be confused on how the whole suspension works any how.. Any help would be appreciated.

Hi m8, it's the ride height sensor then(easy to replace).......if u want to know more just download RAVE and read SLS description and operation and search this forum for SLS/air suspension threads......u'll get much wiser