Sweep2 produces open polysurface w/naked edges. Prevent? Fix?

How would I prevent this from happening? How can if fix it if remodeling was not an option?

Sweep2.3dm (415.4 KB)

extract those surfaces and run matchsrf to positional continuity, then rejoin.

you may need to untrim, or shrink trimmed surfaces to get match to work as it does not work on trimmed surfaces.