Questions about the 97 Range Rover

My family bought a range rover a few years back from the rover dealer as a certified vehicle. For the most part the rover is a beauty to drive, but through it's lifetime with us, it's continuously had problems with the hydrolic suspension. It's been back to the dealers 6 times already with the same problem where the suspension will all a sudden "drop" while driving, causing major discomfort for those onboard. We're thinking that this car has got to be a lemon, but the dealership wont give us the service records for the car prior us purchasing it, and we basically just want them to fix the problem once and for all or give us our money back.
What I was wondering was, if anyone knows about any Range Rover from that year with the same problems, or any other suspension related problems, and also if there was a recall on that car? I'd be greatful for any feedback regarding the matter, and if so what were your solutions to the problem?
Thanks