It would be perfectly reasonable to ascribe errors to experimental error since an accurate clock was only developed much later and the standards of weight and length were actually not standard.Newton was indeed wrong, because he did not take into Relativity into account. Accurate measurements of motion and Newton's equations predictions showed errors even in his time BUT they were ascribed to experimental error and it was felt that the errors would vanish when measuring instrumentation improved. That was not the case and more accurate measurements simply verified the errors.