If I play with my cards for a while, doing some shuffles, what not. The cards get "stuck" on two positions, I mean, they get either curved and if I push the cards to the opposite side of the curve, it goes to the opposite curve and gets stuck there and I need to wait for the cards to get soft again (Don't know if I'm explaining it very well, tell me if you need further explaining"). How do I stop the cards from getting stuck like that, and how do I prevent it in the future?