Convert it to polygons, I've never used a mesh to render with in Houdini, so I guessed that was what was doing it. On your convert node use the option interpolate through hull, for the optimum amount of polys. I believe since the render engine converts to polys, it was getting confused with the mesh.
Also if you have these type of problems, make sure your face normals, are going the same direction as your point normals. Sometimes they can get flip flopped depending on the geo. Your seemed to be that way with the mesh, which is why I converted it to polys first, since that gives every face a normal, unlike mesh's or nurbs. Displacement is dependent on the normals so if your faces, or point normals are funky then that is a likely culprit, even if your shader has the normals normalized.
BYTW, nice use of the lock node, lol, I've never seen it used like that.