my first duck (hatched a full day before the rest) did the same thing, she had her upper body out of the e g g and I could see she was still attached at the belly. I went to bed at 9pm (on the couch next to the incubator) and when I woke at 1 am she had finally kicked the bottom half off. There was a little blood beneath her. I went back to sleep and by 5 am she was stumbling around the incubator. The other ducklings were more vigorous than she when they were first born, but she's just fine now. I would leave the shell on and wait, I'm sure she won't be stuck!