Put the summary of the bug you're having here

What I expected to happen was...:
Save the world exactly how I left it.

What actually happened was...:
Doesn't save correctly, as if 5 minutes of building never happened.
Steps to Reproduce:
1. Start a world
2. Place a block or remove one
3. Save and quit
4. Go back on selected world
5. Block removed is there, block added not there.