Question for injector builders

[steve604]

I had a low RPM miss appear on my engine after a slightly rough night of burnouts. After some troubleshooting, I found that the problem was with an injector itself. My injectors are 160/30 single shots with 9000 miles on them in an '03 engine. The solenoid is fine and it appeared to be working fine when running with the valve covers off. I decided to tear the injector down today and found a broken/shattered dowel pin inside. The pieces had found their way into the tip and were blocking fuel. Anyone know what would have caused a dowel to break? Defective part or assembly error?