Hi I have a Fiat 500 2011 semi auto, I took in to get a gearbox rebuild and clutch change, it got done but when i went to pick it up, the car was literally jumping up and down when trying to move off then it stalled, the company have now changed the clutch and gearbox and it still does it, and also they have checked all the computer inside the car and can’t find the problem. Do you have any ideas on what could cause this?