I thought the furnace was broken but it just has no indication that you don't have enough ore to process a bar. Still, it seems to have a bug where multiple GUI opens up. I think all UI should close with ESC key for now, until you can unify and only ever have one panel open and never have control of the character while a UI panel/form is open. Sometimes a UI instance will cover another's button. Big no no. User Interface overhaul might actually make this a way better experience to test.