What is possibly happening is the structure becomes unstable at that point.
The static solver may not be able to find a stable equilibrium past that point.
You could try solving the model in either Transient Structural or Explicit Dynamics.

It might also be that a 3D disk wants to buckle out of an axisymmetric shape at some point so a 3D model will give different results in a Transient Structural or Explicit Dynamics solver than the 2D model.