I wouldn’t say it’s fully normal, but it’s not unusual either. I suspect there is a small hole in the membrane, which caused it to collapse. It could also still be malpositioned, and the pressure you are seeing on the membrane is it’s butt, or a knee or foot. But once you open the shell more, it has to stay moistened or it will dry hard around the duckling.
Are you still seeing good activity? How about the yellowish fluid area?
It’s a fine line, when to intervene, and it’s even more difficult without actually seeing it for myself. I just don’t want you to open it prematurely.
bwahahaha.