I know luck is a thing, but I truly think there's something wrong with the fresh/old calculation when an egg is on the verge. Twice this week I hatched 7 day old eggs that were marked as fresh in my hatchery. Both times the 3 I hatched were at the top of my hatchery list, meaning they could have swapped to old at any point (they didn't before I hatched). Both times all 3 failed. I've gotten a fail or two throughout the week with other eggs that were 6 days old or 7 days old but farther back in the list, but this seems extreme.
I think there might be some slightly different math going on between what shows as fresh in the hatchery and what's calculated as fresh when actually hatching. I could also have gotten INSANELY unlucky twice in one week, but the fact that this only happened on those eggs makes me at least want to ask someone to take a look at it.