Staad Foundation Advanced: Control Region Issues

I am trying to model a simple mat foundation with 1 control region.

After meshing by following instructions, I analyzed it and the modal displacements, stresses and bearing pressure did not look right.

My slab thickness and soil properties are identical in the boundary and control region.

To verify that is was the control region, I deleted it then remeshed the boundary and analyzed. The results looked good without the control region.

Any idea why the control region makes is messing up the analysis?