I have a simple test program, MeshViewer.java, in toys/FX8-3DAPI to illustrate this bug. The reproduce the bug simply uncomment the following commented out lines and comment out "computeMesh(...) in MeshViewer.java:

                        // File: This is a bug.
// triMesh = buildTriangleMesh(10, 10, 0.5f, 1);
// meshView.setMesh(triMesh);
                        computeMesh(120, 120, 0.5f);

Then compile and run the program. You should see a rectangular mesh rendered in line mode. If you press "1" you should expect to see a less tessellated mesh but you see nothing.