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.
Its an old 1800s barn with an upstairs, thats where the staves are. Im going to haul them down. Its never been this hot before. This is crazy. Im worried I may not save some of these and they were perfect. If they are ruined Im not going to the salt flats this year because these staves were for that.