What should happen is I should be able to remove blocks from a furnace and add fuel, but there is a bug preventing me from doing so.
The bug disables the player from adding fuel to a furnace or removing blocks from a furnace.
To trigger the bug, simply
1. Make a furnace
2. Place a ingredient in the top slot
3. Attempt to add fuel, or remove the ingredient from the top slot
4. Only you can't remove the ingredient or add fuel