Hi Jean-Paul, it seems that your revolve has a bit of skew in it, probably that is not good for the offseter.

If I take a look at the edge of that revolved surface:



If I then zoom in to the top view of that edge and look at the back end, I can see that it is not aligned to the world axis line:



the front part of it is though. So it is either rotated or it twists slightly instead of being a simple world-aligned profile which is more what you'd want.

In fact, looking at it some more, it is just the one endpoint (the one at the back) that is off of the world axis, so that means it is not actually a planar profile, it has a slight twisted shape to it. I'll see if I can repair this for you which will probably make the surface offset work.

- Michael