Hi Burr, yeah a trim curve that is non-planar goes through a much different process than a planar one, it tries to get the curve onto the surface by a process of pulling it down along the surface normals, but that process in the geometry library only works very well currently if the curve is really pretty close to the surface already. If it's a fair distance away it tends to make squiggles in the curve. I've been planning for quite a while to overhaul that particular "pull down 3D curve to surface" mechanism.

- Michael