Summary:

Blocks break with a delay when the player in the creative sneaks.

Steps to Reproduce:

1. Make sure your game mode is set to creative.
2. Sneak (hold shift).
3. Start breaking blocks (need to break without ceasing; without stopping moving and sneaking)

Observed Results:

Blocks break with a slight delay.

Expected Results:

Blocks will break without delay.

Video:

Minecraft 2021-01-30 19-22-15.mp4