What's the version number of MB (Help > About) that you're using. I seem to recall, although I may be wrong, that this was addressed recently. Mine is not behaving as yours. Neither for odd nor even number of tracks.
You might try narrowing the window to the point where the tracks are in one column, and then make it wide to the point where you have two columns. I don't know if that will work, but it's worth trying.