The Bug

When breaking a block that can be instantly mined (like torches or decorated pots), if you keep mining the block behind it, the breaking animation of such block freezes. Also, besides freezing, it is also accumulative; so you can do the same thing over and over until the block finally breaks (and when it does, it breaks with a delay). It only happens when you keep mining for less than 1 second. If you keep mining for more than 1 second, then the breaking animation will reset as expected.

This can happen with pretty much any block that you can break instantly. So it also happens with dirt or sand if you use an Efficiency IV shovel and the block behind it is somthing harder like wood or stone.

How to reproduce

1. Place any block that you can break instantly (with or without tools)
2. Break that block
3. Keep holding the breaking button for no more than 1 second