I had the same thing happen to me, i tried sinew and leather, super glue, kwick it and it still grew. Finally broke and the I saw i had a dry glue spot under the crack (looked like right where the clamp had set) yet both edges had held. This allowed the belly Osage to disconnect with the boo. After separation belly wood was at the mercy of nature and its own weak violated back. Can't say This was your problem, but hummm could be.