A couple of months ago we laid prefinished 3/4 inch by 3 1/4 in red oak flooring in the master bedroom. After we were done we noticed a buckle that was about 4-6 feet long. Unfortunately it isn't under the bed and easy to ignore. It is not due to moisture. I can only assume as we got close to the end of a run near one wall we ran out of staples and didn't realize it. When we got the next course nailed it pushed it up. Any suggestions?