When I lockdown I don't care if a chick pops out that day, I leave it in lockdown till the end of the 21st day. I leave any early hatchers in there to chirp away to encourage the others to pip. Plus them running around bumping the eggs helps get the others to get the show rolling. Now if I have say 30 hatched and 6 not even pipped, on day 21 I'll quickly pull out the tray, set the 6 back into the hatcher and move the 21 to the brooder. Then I'll give those non hatchers a few more days, if not out by then they are going to make it into my brooder. If there is one or two that have pipped, I'll leave the door closed to give them a better chance. I've opened it before and they got shrink wrapped and died in the shell, so no more of that. Just do what works for you, learn from your errors and keep on hatching.