> What about the broken edges from the one rail sweep using
> both end lines?(as shown in the pics)

Well, it looks weird but it's similar to the 2-rail sweep case - if you use a rougher curve you can see that you get a kind of individual sweep piece along each segment.

When you select both end lines, that basically makes the sweep do a type of gradual morph between the first shape and the second shape, as things travel along the sweep.

So that shape morphing combined with the added rotation as it steps from one segment to the next, makes it unlikely that the separately created pieces are going to line up.

Things do line up if your rail segments are tangent where they touch, so if they are pretty close to being tangent, they get pretty close to lining up but not quite.

If you use that same segmented sweep sample file I posted earlier but with just 1 rail used you can see how the sweeps are created on each segment individually:





So you're getting the same kind of thing as that, just with smaller gaps due to the smaller angular difference in that other case.

- Michael