The bug
When I mine blocks in Singleplayer (survival or creative does not matter) it disappears, but it takes a little bit till the item drops. It works in Multiplayer as it should.

Steps to Reproduce:

1. Create a world
2. Mine a block
3. Wait till the item drops

Observed Result:
The block does not have any black particle effects when you mine it, and the item does not drop instantly.
Notes:
This bug affects any worlds I create.