Computer simulations of the orbits of these three planets seem to suggest that they are in a 'chaotic' state, particularly Neptune and Pluto. What this means is that, in addition to Neptune and Pluto being in a roughly 2:3 orbital resonance pattern, the orbits themselves are far more complex over time than a simple calculation from Newtonian Physics would suggest, over the span of many orbits. This doesn't solve all of the mystery of the previously reported deviations in their orbits, but it suggests that the need for a Planet X to account for them is not as great as it was once thought to be. In other words, the deviations fit the model of a chaotic system better than they do the need for a more distant perturbing body in an orbit very highly inclined to the plane of the solar system.