Partially initialized block bug

What I expected...:
After traveling in the Nether, save your game and try to open a furnace. 

What actually happened...:
Game crashed, furnace and nearby items disappeared (world partially regenerated) 

Steps to reproduce:
1. Use 4 furnaces at the same time (there was a ton of items around when the bug occurred, so this may also be a condition.)
2. Enter the Nether and return
3. Immediately after, go near 4 working furnaces, open the game menu and try to save.

4. If the game crashes and the furnace and nearby items disappear, the bug has been detected.