Hey Stick,
That stave is full of bug bites. One of which is clearly visible in the 7th pic down, of the tip. That dark spot along the edge, just under the ring that is your back, is a bug bite running across the stave, and the thin dark line extending from it on either side, is the tree's reaction to the damage. I saw alot of dark figuring in the the rings of the handle/fade area of the belly, which is also likely the result of bug damage.
When the bugs tunnel between the summer wood rings, it can cause the stave to de-lam between the rings; and it weakens the wood and makes it act more brash & brittle.
There is no good reason in the world to ever have to back a hickory bow–even with violations, so it makes me think you might've missed some subtle bug damage in your earlier attempts that failed.
–John