1. Lack of axis rotation
2. the ball is grabbing early and burning out.
3. Lack of ball speed
4. Lack of revs
I can attest to all of thess.
(disclaimer - I'm not a coach)
With my skid-flip ball, I find also that too much speed makes it skid past the break point.
You have to have the right ball and be precise in aim, release technique, speed, and follow-thru (follow-thru ensures that the release is consistent and the axis rotation and revs match the chosen breakpoint).
Also, the oil must cooperate. By following the inside line you're basically trusting the oil to assure a skid until a specific exit point, e.g. 40 ft, and if the oil isn't there, either due to light oiling or pattern, or due to previous bowling, - or if it's too long to allow the ball to react strongly off the oil - you're toast.
"If it ain't workin', you're either throwing the ball wrong or throwing the wrong ball."
"Follow the oil!"
"Dry lanes ain't worth a shot!"
"I love the smell of lane conditioner in the morning!"
current avatar is Gabby Hayes. Looks a lot like me!