Yup, I have the same problem with my BX MMM (60 incher). I played around with it for hours and couldn't get it to lower evenly. Tried adjusting the spring balances, the adjusters on each side as well as the long threaded rod that goes back to the rear right of the seat.
The deck is level when down, but raises and lowers unevenly. I sure wasnt impressed with the adjustments. Deck still mows just fine though. no complaints there! Im just left wondering if I bent something somehow (like maybe the front link from mowing on an incline) and dont feel like I should have to take it to a dealer to adjust something that should be well within my abilities. Kubota needs to publish a new procedure for getting this right or theyll have a lot of unhappy owners.