This has happened to me once before with seemingly no cause and has happened to happen again, for a different project completely. So, when I go to render my scene, it looks great in Eevee, however the mesh renders broken in the Cycles render and shaded viewport, either CPU or GPU. All of my normals are calculated properly, I have no n-gons (only tris and quads), and my scene scale is above decimal points completely because I thought that it might be a precision issue. Anybody have any ideas or should I open a bug report?
Update: I also tried appending everything into a new blend file and that also did not work.
Update 2: it was the displacement modifying the mesh when it rendered. I’ll leave this thread up so that people can hopefully find it if this ever happens to them. To fix, cut the line between the shader’s displacement node and the output node. This is easy to miss if you use Blenderkit or Lily Surface Scraper.