Thanks for the file. It seems RailClone is having a few issues parsing that spline, probably because it is quite complex. The solution appears to be to change the spline numbering. Just pick a vertex in the large boundary spline, right-click and choose Make First
to change the order. I found that picking on in the notch on the left of the roof worked well.
I hope that helps, please let me know if you have further questions.