Is there a lock on the twist dial for deck height
If it's like the JD there's a visible aluminum ratchet block underneath the adjustment dial.
On the JD it's directly under the switch control panel. The locking mechanism can get hung under pressure, or the lock shaft possibility broken, keeping the deck lock engaged.
I keep mine unlocked and drop it to the lowest setting for transport on the trailer. When hauling it, that's a lot of weight constantly hammering that lock mechanism.
