BBismuth ore being smelted with no smelters assigned to it

So, i noticed that my smelters, once i finally found a bit of bismuth ore started consuming bismuth, despite not having any one of them being assigned to smelt bismuth bars, i had to remove all smelters from being on duty to (and all other smelting) to stop.

Smelters and miners will naturally move to other ores to smelt/mine if what they are assigned to has finished.