Problems with squishing a non-developable surface

I am attempting to squish a surface on the face of an ellipsoid so I can use “squishback” to convert 2d items onto the ellipsoid. For some reason, Rhino is separating my surface into two parts and squishing one into a mesh surface (what I want) and the other into a surface (similar to what would result with the smash command). Because of this, I can only use the squishback command on the half that is meshed. Has anyone else had this problem and how can I overcome it?

Can you post a .3dm file with your example?