Why do I get this Naked Edge?

Everytime I add that inner circle I get a naked edge. Everything seems fine, I have joined and all lines are inserted with the osnap, so I have no know idea why I get this edgeNakedEdge.3dm (193.8 KB)

Using gumball you can drag the objects around and you should see three objects.
Two are closed surfaces and one is just a revolved surface.
What you are seeing is the edge of the revolved surface.