Like Brian said, the profile curves weren't closed and your rail curves needed alignment.

You can see the status of a curve by selecting it and looking in the top right to make sure it's closed.



The best way to avoid this is to use snapping to make sure points are where you want them.

File attached with updated curves in a new Style layer:

Simba,
A couple of the others have pointed out some issues.

Here is a video of cleaning up the curves:



I also re-visited your last post and noticed that the profiles weren't planar and added that to the end as another operation. (In that end, second one, I forgot to make the bottom points planar with the align tool after I moved them. This can create a non-tangent area that would need to be address)

Must be cleaner in the generation of your curves.

Also, your working way out away from the origin? If your working on some very large space station or something that requires that, it may be best to create your parts at the origin then assemble them into place far away later...