Kia Picanto Automatic gearbox fault

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Hi, I'm having some problems on the wife's kia picanto. It's a 2007 Automatic. The problem occurs once the car has been driven and warmed up. When pulling off from a stand still, there is a shove/ jerk that pushes you forward rather than gently rolling forward when cold. Tried flushing the gearbox fluid and replacing with fresh, but not sorted it.

Any ideas ??