Transmission Not Go Into Gear problems of the 1999 Audi A4

While driving in cold weather vehicle would be jerking & bucking like a stick. Transmission would hesitate when shifting into another gear after slowing down & then speeding up. Vehicle been to two different dealerships. Nothing found after diagnostic test and test drive. Vehicle was leased. Arbitration not working. Problem is intermittent. Request for replacement denied, despite physical test that shows the error.