The window crack discovered in September is believed to be caused by an external impact: https://www.sfchronicle.com/bayarea/article/Something-hit-Millennium-To

The window crack discovered in September is believed to be caused by an external impact: https://www.sfchronicle.com/bayarea/article/Something-hit-Millennium-Tower-and-cracked-window-13276821.php https://www.sfchronicle.com/bayarea/article/Something-hit-Mi... There was another one discovered in late October, but I haven't seen any updates on that one.