I'd give them a shot. There are two big risks from cracked eggs. One is that bacteria can get inside and multiply. Bacteria might not get in at all. Or if it does, it might not have enough time to multiply and cause harm before they hatch. There is a chance it will kill this chick if bacteria does get in, but it should not explode before the hatch is over. This is the risk I would worry about but I'd take this risk at this point.
The other problem is that the egg could dry out faster with the shell cracked. Since you are going into lockdown, you are going to raise the humidity anyway, so this should not be a problem. If it were earlier in incubation, it could be a serious problem.
Some people put wax on a cracked egg to seal it back up. You don't want to coat the entire egg with wax if you do this because the egg shell is porous and it needs to breathe. Going into lockdown I would not do this, but this is always an option. I don't think it would hurt, I just don't think it is necessary at this point. I'd think if bacteria is going to get in, it is already there.
Obviously this is not a desired position to be in, but I think they still have a chance. Good luck!!!!
