The sound of blocking with a shield is only hearable by other players (not the person blocking)

The bug

There is a 'shield blocking' sound when you right click to block with your shield. However if player A blocks with their shield, they cannot hear the sound; only player B standing nearby can hear it. (The sound apparently does not play in single-player.)

Code analysis

Code analysis by Marcono1234 can be found in this comment.