Automatic Kia Picanto Box Problems

Good morning my mother bought a Kia Picanto New Agency has apparently behaved well until approximately 1 year ago that began with a failure, suddenly the box is stuck or stops, and when starting it it gives a strong blow, it has penalty has 100,000km. I thank you for your collaboration since it has taken it to several mechanics and tell you that these cars usually have that fault and have to make the box.