The bug: 
The punch sound plays for every time you press the attack button, regardless of how many times your character actually swings. This results in the sound playing out of sync with the punch animation. Only the punch sound is affected by this bug.

How to reproduce:
Press the attack input as fast as you can over the course of a few seconds. The attack sound will play more times than the player model actually attacks.

Minecraft 2021.03.06 - 15.50.13.14_Trim.mp4