Ducks are nothing like hatching chicks, they take what seems like forever to completely hatch. Once pipped tey rest, they zip and rest and push and rest more. Then thy tach and rest again. That duckling wasn't exactly ready by the looks of the veins still appearing large and full of blood. To keep opening the ator is to drop humidity and maybe shrink wrap those not yet hatched. That one looks lie the membrane is covering the nares though,which would interfere with breathing.