I used to have this problem as well, and was always afraid to use anything with a lower pin position.
I'm convinced it's because of the asymmetry in the ball. Since using almost all asymmetrical equipment, I have never rolled over a finger or thumb hole, then again I do have a lot of tilt.
IMHO, It's the ball.
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Ah yes. I have my temporary driver's license - and - my astronaut application form... I didn't pass that though, I failed everything but the date of birth. -Steve Martin (The Jerk)