Rhino 6 bug - bad mesh

The following screenshot depicts bad mesh. It is made of a mesh and a triangle. I cannot select the mesh, but I can select the triangle. It takes about 4 seconds to move this mesh with the gumball. I made the mesh by extracting it from bigger mesh with ExtractMeshPart command.

When I use RebuildMesh command, the triangle disappears, but it reappears when I move the mesh with the gumball.

bad mesh.3dm (110.9 KB)

Hi Andrew - did the original mesh have an offset, ‘Thickness’, applied?


no thickess, no offset
The original mesh is here: bad big mesh.3dm (169.1 KB)

Yeah, this mesh does have displacement applied, not thickness, I did not check that on the original piece. If you turn that off in Properties, both behave normally as far as I can see.