I wondered if it could be something about when you opened the incubator to take out the other chicks. But that doesn't really make sense, given that the humidity was high before and after and you were fast about it, and considering how common it is to take chicks out quicky and have no problems with later chicks that are still hatching.
I suppose it could have gotten shrink wrapped during the time you were assisting, but I can't see why the membrane would dry out in the part of the shell farthest from the opening, so that doesn't really make sense either.
So maybe something specific to that chick and it's development, or maybe just bad luck. Neither of those would be anything you can control. But you may want to keep track of which chick this was, and not breed from it when it grows up. I say this because of how late it was at hatching, not just the shrink wrapping. (Speed of development, and ability to hatch without assistance, are partly inherited.)
You said you kept finding blood when you tried to assist, so that would mean the chick was still absorbing the yolk at that time. But this was after all the other chicks had fully absorbed their yolks and finished hatching, so this one was definitely running late. That makes me wonder if it had something wrong (in addition to the shrink wrapping), or if it is just slow to develop.
