Sounds rotten to me.I wouldn't take a chance setting it with the rest of your eggs. How do the rest of them look?
Just for learning purposes, I would take it outside or into a very well ventilated area and open it up. Take pictures to show the seller - maybe they will reimburse you, but don't count on it. If you want to PM me the seller's Ebay ID, I'll look in one of my groups and see if others have had a problem with that seller.
The rest have detached air cells.Who knows how old they are!