hi my p38dt seams to drop down a few inches at the rear whiel going along.as soon as i stop it corrects itself?.started her up this morning and imeadatly the accses moad light was on acompanid by the standerd ride hight light and it took a good 3 minits to get itself up. when put up to waiding hight it takes an age to get there. this has all just suddenly happend. carnt find any leaks,and it had a new compressor larst year.any idears?thank you.