On the 8 pins, you just got a little "hosed", so to speak. To leave the solid 8, you have to get the head pin moving fast enough to come back from initial contact and still beat the ball to the 5pin. The 5 will get trapped behind the head pin and go straight back, missing the 8 on the way by. Just bad carry/luck.
The 9's however, are a bit different. They happen when you have relatively good entry angle, but little to no deflection as the ball enters the rack. The ball rolls so strongly through the pindeck that the angle of entry + the strong continuation cause it to hook past the 9pin, and leave it standing, unless you get lucky and something else hits it.
A strong finishing ball, when thrown just a hair too slow, or just a hair high in the pocket, can be a 9pin machine. It has been my experience that a strong finishing ball has tended to leave more 8pins for me as well. Not nearly as many as it did 9's, but enough to say it was a property of that ball that other balls didn't tend to have.
I have a ball that I love. It knocks the CRAP out of pins, Butkus it will also leave a few 9's, and some occasional 8's as well. I'll take it though, cause I know that this ball is hitting hard and moving pins well. I've thought about adding a small flare reducing hole and adjusting it slowly, but decided not to. I'd rather deal with the occasional misfire than take a chance on "over killing" the ball.
One thing you might do is SLIGHTLY adjust the surface to let it bleed off a little more energy before it gets to the pindeck. That will change the entry angle a bit, may change the initial launch angle, and probably help with the deflection as well, as long as you get the surface right.
