Yeah you guess it. It's your boat name geometry . Apparently the MR approx node you assigned to it doesn't like it very much, my guess is the gaps between the letters are throwing it off. Also I don't think that piece of geo needs it as 1. its not built for smoothing and 2. It's pretty smooth looking as is.... so I unassigned it and the problem went away. I even triangulated the mesh as the error suggested and the problem went away.