Parametric sweep modifying component definitions and materials

I am modelling a simple parallel plate capacitor in 2D with plate length "L" and air gap "d". When I set up a Parametric sweep over the variable d and run the simulation, the geometry, materials, and boundary conditions of the original component become modified.

For example, before the parametric sweep computes the gap material is "air", but afterwards when I check the materials I find that the gap material has become "aluminum" (the material of the parallel plates).

Is there a specification I am missing in setting up the parametric sweep, or is this a bug?

Thanks

Evan