When you have a furnace and put some items in and then put a whopper on the top and drop some items in the whopper the furnace will get cleared -> all items are away

The other bug is, when you put a whopper next to furnace and then put some coal (for example) in the furnace (burn place) and then put into the whopper on the first place wood (for example) and on the second place coal, the whopper won't fill up the furnace.