How to weld two overlapping edges of an untrimmed surface?

Hi! I have issue with this tube (see attached .gh with internalized surface).

Is there any way to weld two overlapping edges of a single surface to create a tube?

I’ve tried to somehow merge those faces, but couldn’t handle it…

problem_surface (1.8 MB)

The GH file is useless. The internalized surface is invalid.

Please provide a Rhino file of your tube with the geometry that you used to create the tube.

Here is the 3dm file.
problem_surface welding.3dm (2.0 MB)

Problem is that all edges are naked, none is interior. And I couldn’t find the way to merge the surface.
problem_surface welding

@martinsiegrist Have you had chance to look once again at my case?

I’ve done some research and it seems other users had similar issues…

Can you provide the curves you used to create the surface?