***Spoiler*** During the progress into Act 3 the game asks you to build in 4 of the NPC's homes, with unlimited inputs for a almost full out put of product, to meet the throughout of the output.
No confirmed fix yet. Players suggest: In the meantime, you can set a splitter to grab anything stopped at the furnace input and put it on a separate line, but it is pretty slow and it's better to just be conservative with the number of level 1 furnaces you…