Yeah, I’ve been having issues with shipped eggs all summer (and first summer incubating!). Quality and shipping stress have been all across the board. Have ordered a variety of breeds from a variety of sellers, mostly from eBay. Try your best to order from reputable people, first off. Ask to have eggs held at the post office and have the PO call you. This reduces at least a small portion of travel stress. When you open the box up, inspect for damage and candle to ascertain where, how big, and how loose the air cell is. Maybe even mark it. See if it is a little jiggly, shifts a little, or can free float around the egg. Candling can reveal little cracks, too - if seen, seal with wax or nail polish. Sometimes you may see other air bubbles - not good. Sometimes the egg shell looks kind of mottled or has too many thin spots - may be too porous.
Shipping can cause damage no matter how well packed. Things can be ‘scrambled’ inside and you wouldn’t know. Loose/detached air cells are not good - they are supposed to be small and sit unmoving in the blunt end of the egg. There’s still a chance they might hatch, just very reduced. I’d recommend letting shipped eggs ‘rest’ blunt end up at least overnight. Some people go as long as 2 days. I kind of suspect eggs shipped from certain regions of the US have a worse time in the PO system than others. Seems for me eggs from down South come in tougher shape. Ones from close by, ie the state next door, get bounced around to way more PO hubs that necessary IMO. Best shape eggs so far seem to come from northern Midwest, for me. I’m mid Atlantic. Also with everything going on with the PO and pandemic, shipped eggs might be having a worse time than usual ...
Sometimes you can suspect the quality of the egg wasn’t good to begin with even before shipping. Large air cells are suggestive of an old egg, or one that is too porous. Thin shells or too porousmight be because of poor hen nutrition. Eggs should not be wiped or washed. Expect some dirt but not a ton. A really dirty egg might mean the hens are not kept in the best conditions, someone slacked off on cleaning the nests! Oddly shaped eggs have decreased chances of hatching - too narrow, too small.
From what I understand, if you get about a 50% hatch rate from shipped eggs that’s pretty decent. Of course many people have much better hatch rates, but many others have worse, too.