It’s a bolt over base or bolt override malfunction. Not great, but not catastrophic. Plenty of videos on YouTube of how to clear one.
Mortaring makes a bolt over base worse. The round is caught between the nose of the charging handle and the bolt. That’s why tools like the leather man mutt have a specific tool for this malfunction to allow you to grab the bolt at the face and pull it back without the use of the charging handle.This. Believe a good mortaring or two will be required. Good example of needing to have a quality charging handle.