I have an issue with air suspension on 2000 discovery td5 it lowers when i start engine from normal height to its bump stops and after about 10 minutes it returns to normal height. I changed air bags about 4 years ago and height sensors at the same time i dont think it's air bags as it holds its height fully until engine has started sometimes it will hold its height for about 10 ninutes and then it drops down and other times it will lower as soon as i start it up. Thanks for any help