A problem with this achievement Smelt Everything

When I tried to make that achievement I put 3 hoppers on top of the oven everything is fine but when I put at the end 3 chests on top of the hoppers individually suddenly rarely those two chests came together and a chest was alone so I made the attempt to make an achievement and I did it but when I wait for that achievement and I do not arrive I hope they fix it very much thanks.