Random in stock items

I’ve been eyeing on this coat and every 2 minutes the sizes goes out of stock and then back in stock in a different size. Anyone knows why this is happening? Like if I go in the app now, a size Medium is available. Then if I go back in 2 minutes, that medium is unavailable now and another color will show in stock or another size with show in stock. I’ve also seen a lot of reviews on Abercrombie sending used, returned clothing to customers. Any chances these random in stock items are used and returned?