I have the same kind of problem on Vitus track. My solution : when I want to export the AIW, I remove the part of upper track that make's the AIW tube is juming (sorry for my bad english...). So the under AIW tube is good, but the upper tube is not, it's falling from upper to under track. After that, I build the part of track I have removed, and export, only the 3D. Then I have to go in the ISI AIW Editor, only to build this small part of upper AIW tube, the function is "smooth path". A little bit complicate, but it works.
I have an idea, for the next time I will have something like that. Instead of make the upper track with track tool, I will make this little part with a wall. But I never try, so may be it's not working.