Sounds like something is hanging up in the deck lift system. I have a 60" MOD and I have never had any problem like that. Look up under the right black body panel below the deck depth gauge dial. See if there's something binding or stuck on the gear that sets the depth, or prevents it from rotating correctly.
Check your pitch anyway because the factory setting doesn't usually have enough pitch when they send them out. Check it with someone in the seat, or add an extra 1/8" of pitch, because it does make a difference. I have checked mine repeatedly with my Deere deck gauge with me in the seat, and out of the seat. That's how I came up with the etxra 1/8" if you have no one to sit on it while you set the pitch.