I think the problem gets into some chaos theory, the kind you see in weather prediction.

When the forecast says "60% chance of showers tomorrow", what he really means is that they ran a few billion simulations of the environment with very tiny perturbations of the initial conditions and in 60% of those simulations, it rained. In 40%, it didn't.

Tiny little changes in any variable in a chaotic system will, in the long run, lead to huge variations in outcomes.

This system with it's 416 planets has one outcome- perfect orbits constantly. But if you add a single 1 kg asteroid to the system, that would perturb everything ever so slightly. That slight change could result in the entire system chaotically coming apart from stability.