Why does SW struggle so much in handling "faulty faces"?

We use SW for mold design, but we don't use the mold tool function and one reason is because of this problem.

The parts for the tools (engine block, flywheel housing, gearbox housings e.tc.) comes mainly from Catia, Creo and Siemens NX.

Regardless if it's a step file or a native file, we will always get a solid after import, sometimes with the addition of a quick diagnostic->heal gaps.

But in 99% of the cases, we are left with "faulty faces", some that won't repair automatically but instead needs to be replaced one by one.

The "faulty faces" looks ok, even if you turn on zebra stripes or similar, but SW considers them faulty and we can't spend a day to repair each time a customer sends a new revision.

So today we use the cavity function, creating a "base part" with the mold block and its cavity together with all parting surfaces to split the different components (core, cavity, slide e.tc.)

This always work if you can get a solid body after import. No matter if there still are faulty faces.

But sometimes I would prefer going with the surface approach instead of base part approach.

So i tried another idea:

- I made my mold base part, and splitted the solid with my parting surfaces to a core and a cavity solid.

- Then i removed all outer surfaces from the solids and was left with 2 surface bodies, representing core and cavity.

- Finally i tried to use the offset/copy surface to copy one of these surfaces to a new part, but SW refuses since it is "faulty".

So the surface is complete, no need to knit anything, only to make a copy, but Solidworks says "NO".

This is really frustrating.

I know that one solution here would be to export the surfaces to parasolid and import them in a new part, but that mean losing the link to the original part.

Why is it so hard? I can still use these "faulty" surfaces to cut a solid, but I can't copy them into a new part.