I don't know if your barn is enclosed where you stored the staves but I lost the best osage I ever cut in a closed-up outbuilding, I had the same result storing staves in an attic. These staves were green when I put them up, not dried. I store my bulk staves in a crawlspace under the house now. I keep what I call my "on deck circle" of bow blanks and a few dried staves out in my shop, it is enclosed but well insulated and never gets below freezing in the winter or up to the outside temperature in the summer, it cools off at night in the summer.