They were shipped, but if they were exposed to cold or frozen, it seems like that would have stopped them from developing at all, not resulted in fully formed chicks that had absorbed the yolk, but did not escape the egg. I could not tell if they were malpositioned. They seemed curled up like the chicks in the illustrations. Maybe that's it, but if so, how would I try to prevent or alleviate that in the future? Regarding ventilation, the incubator has a fan and air holes.
Maybe I will try the dry incubation method - but, where I live, the ambient humidity is often in the single digits. I read something about skull deformations related to dry incubation - is that a risk?
I will try local eggs for the next batch, when I work up my courage, again. Others, though, had successful hatches from eggs shipped from the same seller about the same time as mine.
Just another thought. Sometimes the shell will harden, I mean harden! The chick can't pip. I have had eggs that I tired to put a knife into and it took a lot to do it! So, I started raising my humidity the last three days before lock down. Helps soften the egg shell. Seemed to work better. Instead of mid 30's low 40's, I raise it to mid or high 40's a few days before lock down.

And yes, too low a humidity, anything lower than mid 30's, which is considered dry hatch now, can cause skull problems, and toe problems. Less toes! Don't let the humidity get lower than 25.