I have the same problem. I get to my fifth load, then when going back to the furnace, seems to stop, says it can't find the furnace, and then quits.
Ran it a couple of times and it worked :)
|_Narcle's AK Smelter_| 1h:39m:39s |
| XP Gained: 9135 | XP/Hour: 5536 |
| Bars Smelted: 513 | C-balls: 0 |

