Click this link to view: https://youtu.be/uLA8ODqtOtU If pattern tracing pin or lens tracing pin can't move up when frame tracing operating, probably the butterfly assy broken. This video show how it being replaced.
How to diagnose lens measuring unit (LMU) problem? If your edger LMU stuck, probably caused by the lens residue (powder) jam the LMU. Click on the video to find out more.