I had a look.
They look a like, your part and the original one but they are not made in the same way.
I think the problem is in the beginning, Regarding "Surface-Loft1" e.g.
- the original file does have start contraint (Tangency to face) and end contraint "Normal to profile", but your part does not.
- Others are also missing start and end constraints.
- I also think there is something to with the "Plane2" in your part, how it is created.
Have a look at my images.
The first image shows both normal to top plane.
Thanks for taking a look Ingvar, and thanks for the pictures. I'll try editing that first loft and perhaps the plane2 and I'll let you know if it works.