A couple of failure to hatch chicks is not uncommon, especially with shipped eggs, eggs exposed to heat or cold temps, eggs that weren’t turned properly, old eggs etc…anything that stresses out an early or ore incubation egg, and while it is a higher percentage in stressed eggs it is also a thing in normal eggs too, just like 20% of early pregnancies miscarry, so too some chicks just can’t hatch. Often you don’t see anything physically wrong, some even pip or zip, but they are just too weak or whatever and just fade away, even if rescued they don’t survive long. I have noticed a trend in quail eggs traumatized by shipping (saddled air cells), the chicks get to lockdown but fail to hatch, when I do the necropsy they look dysmature (the size of their age but lacking most of their down, features not fully formed, looking like a larger version of a younger embryo), obviously a developmental issue but it can approach 25% of the hatch! But no, there is nothing you can do to fix or prevent it (besides preventing the stress in the first place) or anything you did or did not do to cause it, it is just part of hatching.
