John Deere JS 48 Mowmentum Deck Issue

I've had a JD JS 48 Mowmentum mower for @ 4 years...Like it...Something is up with the deck adjustment. When I move the lever to the highest setting, the rear of the deck is much higher than the front of the deck and when I mow, it is clipping the yard @ more than I would like, i.e, as it it were at the lowest deck setting? I believe something with the deck raising system has gone awry? Any suggestions would be very much appreciated.

Thank You.

MTB