It's hard to say what happend. It is the first bad report I have seen on a shockwave though. I believe anything mechanical can fail, but without knowing if your bow was tuned, the exact location of the hit, the angle etc, I can only take your word for what happend. I am glad you recoverd your deer. I do however suggest you check each and every head, and make sure the blades swing open freely. I am not anti-mechanical by any means, but that is one reason I prefer fixed blade heads. The thing is this is bowhunting and stuff can and will happen.

TAKE YOUR KIDS HUNTING AND YOU WON'T BE HUNTING FOR YOUR KIDS