Pluto was not nearly as large as astronomers were expecting.
Mass found to be even less after Charon was discovered.
Scientists have since gone back and measured the discrepancy the Lowell, Pickering, and Ketakar found in Uranus' and Neptune's orbit.
The perturbations simply disappear when one uses the more precise masses found by the Voyager flyby.
Ultimately, it appears that observers were quite lucky the false predictions were quite close to a real object
