i was out shooting and took a normal shot and mised by several feet with crazy flight.  the arow passed through my carpet backstop.  i was extremely disgusted with my shot and couldnt belive that i could miss the whole bag from 20.  
when i went and found the arow i realized that about six inches from the tip the shaft was completly severed, the only thing holding the carbon together was the wood grain fabric.  i am convinced that this is what stoped it from causing more damage,  not shure why it broke there was no visible damage.

I had this happen to me a week ago. I found that one of the weights I had inserted, a small section of brass all thread rod, had come unglued and shifted up inside the shaft to the center of the arrow. It caused a radical flight and when the arrow hit it sheared the shaft right in half.    

Note to self: MUCH stronger glue.