For some reason, the furnace output is getting stuck, indicating as "full" way below the stack limit (I've been testing with copper plates specifically, and they're only getting up to 4 before it stops). Not entirely certain why, though, as I've checked the mod's scripting and I can't find what would be causing it.

EDIT: This is direct-smelted from the ore, mind you. I haven't unlocked the advanced processing variants yet.

I think this is a limitation of the prototype itself, as with this setting turned on furnaces are seen and work like assemblers.
And assemblers never reach the stack size of the item they're working on.
_77

Oh, right...well, frick. I suppose there's likely no solving that. Thank you, anyway!

Try creating a mid storage at the beginning of the bus. I usually do this.
(At least when playing with loaders.)