When the old cobbler and his Wife are coming to investigate the noise the elves are making, all the elves run out the door.
There are more than 12 elves that run out the door, although there were only 7 birds that turned into the elves originally.
When the shoemaker tosses the crust of bread out the window, there are seven birds, who then turn into seven shoemaking (shoe repairing) elves. At the end, when the shoemaker wonders whether the birds might have had a "hand" in the "miracle", only five birds are present to answer the question.
When the elf wipes the smudge onto his shirt, the smudge seems to float in the air in front of the shirt, as it doesn't move with the shirt and part of it is actually in the air.