They will often bleed out or sometimes drown. There is not much you can do but read the guide to assisted hatching. The internal pip is very early with ducks and they will go up to three days after external pipping before they hatch. That is much too early to take them out of the shell.
If you see liquid in the pip, you have to clear it as best you can. That is one reason why eggs with air cells like that are more work.
I've read it 10+ times and have made my dh read it. OK so try to stop the bleeding and keep liquid from the nose. I got it. How long after internal pip should the external be for ducks?