Ok, don't worry about failures, you are still new to this tillering thing.
I had a lot of failures early on in making bows. Still do once in a while.
Maybe on your next bow, don't put in so much reflex. Also Hickory is a very strong wood.
Were you at 20 inches on a long string?
When my bows are done, the outer 2/3rds of the limbs are flat at a 6.5" brace.
Same bow at 32 inches on tree.