Thanx for uploading. I looked into it and found the problem.
The error occurs when it tries to smooth the lift. precisely it's the curve that leads from the straight upslope to horizontal. There the handles of both vertices sit at the exact same spot. As the program needs to find the distance and direction between those handles, it crashes (as there is neither a distance nor a direction if both points are in the exact same position). To get around this move these handles closer to their coresponding vertex. Alternatively you could just split the segment. If you now smooth, it will work.
In general you should be using more vertices. Especially on those s-curves you have there. Split them in the middle.
Also you should try to smooth the track out by hand first. If you feed this into the smoother, you won't like the result too much.
Buster.