it could be due to a close shot, and speed, can cause funny things with bullets designed to hold together at longer ranges!
hitting that bone at speed maybe caused it to come apart
I have used accubonds as well and had very good results with several calibers, but all my shots were farther out there as well, 200+ yards on most! and still went right thru no issue's(some over 500 yards and still no issue with going thru
some times up closer shots again do funny things with bullets at there near max speed leaving barrel
I have seen MANY ballistic tip type bullets, NOT pass thru a deer at POINT blank ranges, when folks wanted to give a deer a finishing shot, standing over it and NO [pass thru, bullets just came apart
so this is what I think maybe your issue was>
you can always step up to a heavier gran head too, which will give maybe more hold together ??