I was playing single player and on my second day, I visited the blacksmith to learn how to make tools. I accidentally smelted the iron ore before he asked me to and the game wouldn't recognize the smelted ore. I had to reset the mission by walking away and coming back. However! When I walked away and pressed okay on the pop up that said something to the effect of "Would you like to leave now and continue later?" I still had the Iron bars in my inventory. The blacksmith gave me more Iron ore so I could do the mission. I have a feeling if I started the task, smelted the iron before talking to the blacksmith, and then walked away, I could walk back in and get another three ore, smelt it, walk away and repeat for endless iron bars!