Component with identical inputs applied multiple times yields slightly different results.

Hey guys 

I created this component which generates a ridged hyperbolic surface from 4 points.

When I apply this component to multiple sets of points, the results differ slightly even though the inputs are the same.

Can anyone help me figure out why?

Surfaces should all be same size, but the distance between them differs.

Also they do not touch the ground, only one of them does.