This has happened to me the 3 times I have hatched chicks. What I have noticed is that their beaks seem to get stuck in the little pipped whole. At first I would help them out by opening it a little for them but they wouldn't make it. When I opened the eggs they would still have their yolk sacks attached. So when It happened the third time I hatched them I left them for an hour. When I saw no progress after that I began to open it bit by bit near the beak. and left them back in the incubator. Every half hour I would take just a bit more. Then I opened it enough to get their heads out and left them in the incubator and didn't touch them again.I guess waiting that long gave them enough time to close up inside the eggs. I was able to help 3 out that way. Now the reason I acted was because I would see others hatch and the ones I helped showed no improvement. I would also mist water in the incubator every time I opened it and my humidity level would only go down about 2%. I handled the eggs on a very warm wet cloth so they wouldn't dry out much. My grandma does it that way with her chicks and It worked me also.