When you are breaking blocks ( I'm not sure if this happens with regular tools) but with Efficiency V. You break blocks and they stay as ghosts but they are actually gone.

Put the summary of the bug you're having here

What I expected to happen was...:
For the block to be completely gone

What actually happened was...:
Ghost blocks for around 5 seconds

Steps to Reproduce:
1. enchant shovel/axe with efficiency V.
2. dig or chop down trees
3. Blocks stay for 5-10 seconds