Nikon f3 with D head sometimes can't hang the shutter.

Connection is not in place. The connection between lens and camera is not in place, or the communication contact between camera and lens bayonet is damaged or stained, which affects signal transmission, so the connection is not in place. A camera is a general term for instruments with the function of imaging through a lens. Ordinary cameras that take a single photo are called ordinary photography (still life photography) cameras, which are different from movie cameras or TV cameras.