The James Webb Space Telescope is being prepared in the Ariane 5 rocket that will soon put it into orbit. On November 22, Arianespace technicians were installing the telescope in the rocket cap when a fastener suddenly and unexpectedly detached, causing vibrations through the telescope structure.According to NASA, the launch date, originally scheduled for December 18, is now postponed to December 22, 2021 at the earliest.
More information is available on the NASA website: https://blogs.nasa.gov/webb/2021/11/22/nasa-provides-update-on-webb-telescope-launch/