There are some wrong accounts here. To set the record straight, that blade and two others (similar events) were only about 200 hours out of CCAD and where the aft fairing skin meets the fwd skin over the spar, some bonehead took heat lamps and lined them up to cure EA 9309 epoxy as a "filler" used to fill & fair the gap at depot. The skin was badly discolored indicating they had exposed it to roughly 600degrees F. That all but destroyed the aft fairing skin-to-spar bond every 14 inches along most of the spar.
So, one good flex up put that skin in compression and a single portion of the skin popped loose. At that point, it's essentially a parachute and off she came. The U.S. Army sucks at repairing blades and composite structures. Both at the technician AND (especially) engineering level.