So I built a super smelter following the popular one made by Mumbo Jumbo for 1.12.2. I built it according to plan, but the hoppers between the chests and the furnaces refuse to accept anything. I checked if any of the other hoppers worked, and there were no problems, so i'm really really confused as to what could cause the issue. Btw I'm using 1.12.2 since it's modded, but no mods should be affecting this. The screenshots are displaying some iron ore just staying in place on the hoppers.