Don't stir the noodles so dry, you'd better soften them. Don't pinch the top too hard when wrapping jiaozi. It is steamed, not boiled. It is water vapor that provides some moisture. Since it is not boiled in water, don't be afraid to squeeze the stuffing and it will come out. After steaming, don't open the cage in a hurry, and then open it later, so that jiaozi can accept more hot air.