Forgive my ignorance but am having a recurring problem with my Civil 3D CAD. I have created a combined surface of a site by pasting different surfaces of platforms together. However, when I copy this with base point and paste to original coordinates in another drawing, a yellow warning sign pops up beside the surface names. All of the surfaces used to create the combined surface are then brought in as well, and also have errors. When I rebuild the surfaces to fix this, a list comes up in Panorama saying 'error parsing value', and a lot of the points disappear. What am I doing wrong? Help!

Thanks