Repairs ZTR50 - Mower Height Changes

I have a cub cadet ZTR 50. Its about 5 years old and I have noticed a small problem with the lever for the deck height. When I go in reverse and then come back to neutral and then go forward the deck height lever will come out and go back in. I would say that 60 percent of the time it goes back to the same height but the other 40 percent it goes to the lowest height. Does anyone know what could be causing this. I keep scalping my yard and its really annoying.