Undoubtedly you have 3 PTO speeds. 1 N 2 N 3
Behind the PTO speed lever is a plate that is attached to the tunnel.
The machine screw that holds it stationary to the tunnel when loosened allows the plate to be moved a bit in both directions and is actually the mechanism to adjust the positions of the selector.
Repositioning the plate will assure that Neutral is actually in a neutral location.
In all probability some slop has entered the equation over time and a minor adjustment is called for.
My MT180D needed that fine tuning as well.
And welcome to TBN.