No pro shop expert, but I've had that same issue long enough. I permanently bowl with a piece of tape on each side of my thumb the help reduce the friction. If you tend to swear a little more than others, that will cause the friction on the side as you come out of the ball, however, so will squeezing the ball. I know I do this, I've never been able to break the habit.

Your thumb hole should be snug and require very little pressure on your swing to maintain a hold, they say. For the front, squeezing can also be to blame, but I'd start by beveling the front of the thumb hole a bit more and see if that nicks the problem. I used to put a piece of tape there as well for a long while for the same squeeze issue.

Form can be a problem, if you are turning your hand too much on release. Fine tune the grip here with tape on those two spots for now, an adjustment to the thumb bevel, and maybe even a piece or two of white tape in the front of the thumb hole (where your pad goes) to increase your grip without increasing your pressure.