Unless proven different by breaking news, THAT is a crack resulting from the recurving process.  3/4" is too thick, with any wood I know of.   I have done this exact thing two dozen times, and it's an easy fix.
Get a plane, sandpaper, double cut flat file, and/ or scraper, and flatten the belly of the limb for a couple inches each side, flat LATERALLY, even, and long enough to matter.  Then cut a 1/8" slat of something beatiful and strong, prebend it to the original curve with boiling, steam, or microwave.  Glue it on and blend it with the limb./  Presto, beautiful overlay, and durable recurves.