I think there is a simple bug when playing notes near the border. The notes from the MIDI file are displayed correctly but when I press them on a midi keyboard they are displayed on the left hand track.
The software recognizes them correctly, they're just displayed in the wrong track.
A screenshot follows:
It's not a problem at all and you really did a great job and wrote an awesome piece of software that's very useful for learning the piano.
Great job :)