I went through the same thing.. tried different spans and different pitches and bevel.. less bevel or a more snug thumb(front to back) will probably help the issue as it did me but then my thumb wanted to hang up every now and then. I finally just said enough and went with it.. if my wrist is cupped and firm the ball will not slip and there is no fear of the ball ever falling off during my swing so i just go with it.. I change my release and how I get out of the ball all the time so I would rather be able to get out of the ball all the time than hang up and toss myself onto the lane.
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16-17 mph,350 rpm,PAP 5 1/2 x 3/8up, HighGame 300 x 3, High Series 808
Book Average 205,PBA Xperience ave180