When changing mesh for a basic object there is an issue when changing to either a rectangle, sphere or cone. In inspector Palette this change will not show, i.e. if you change a cylinder to a rectangle the Mesh property will still display cylinder.

In the scene view, when changing to  either of the three meshes mentioned above, the object will become invisible. It is still selectable but not visible.

In the Viewer it will display correctly with the newly selected mesh.