To be honest, I've had all sorts of problems hatching this year - none of them (including ducklings) have just popped out without me helping so I was beginning to wonder whether I just intervene too quickly. If they've pipped, I help and have got out 100% of the ones who managed to pip. But unless they pip, I figure there's not much I could do.
With the Orps, most were fertile. I can't remember the exact figures but I think the broodies ate a couple and there were some infertile ones so I was realistically only expecting to hatch about 12 or 13 by the time they got to 21 days. But, yes, by that point only five made it out so it was about seven who got to full term but couldn't get out (and interestingly the buffs were the worst - I had six eggs of blue/splash, lavender and buff and ended up with three blue/splash, two lavenders and no buffs).
H