Size of Face wrong when importing STEP-File

I wrote a Python-Script that lets me select an objects face an than morphes a given structure onto that face, so that there is no overlap over the edges.

Visual example of how it should work:

  1. Box created and exploded in Rhino

  2. Parameter space of selected face

  3. Result of the described script running

And now the problem:
If I export the box from 1. as an .stp file and import it afterwards to use the exact same script on the same face of the box, the result is as follows:


Parameter space of face from the imported box:

The parameter space of the imported box seems to be wrong, so that the morphing overlaps at the edges of the face.

Do You have any Idea what causes this behaviour and how I may fix it? The problem also occurs with .stp files I created in Fusion 360, the morphed structures always overlap at the edges.

I found a solution to my problem:
the import changed the type of the surfaces from “surface” to “trimmed surface” and that seems to cause the dimension deviations if I understand it correctly. After running “shrink trimmed surface” on all imported surfaces everything seems to work as intended again.