chow Unfortunately, there is not enough information for us to understand what you are trying to tell us. Please tell us when you got the error message and what you were doing at the time, e.g. when you imported skeleton data files into Unity, or when you instantiated a SkeletonDataAsset in the scene, and so on. Also, please tell us if the other skeleton data works correctly, and if not, what are the differences specific to this skeleton data?