Can AUDI repair the vehicles they sell?

My two year old Audi A4 Allroad with less than 50000 km on the odometer, has been into the dealer 6 times since August for the same issue. The vehicle suddenly lost power, and the engine management light appeared on the dash. Audi Assist towed the vehicle to Audi Northcliff. The following Tuesday, the service advisor told me they'd tightened some hoses and all was OK. i drove the car 80km and the same problem occurred. This time they told me they replaced a hose, and the problem was fixed. A week later, the same problem. This time they told me they'd found some cracks on one of the Turbo blades & they replaced the turbo.This time they gave me a courtesy car for the week. 500km later and it happened again. I was promised a loan vehicle which never materialised.They replaced another part, and drove the car for 500km before telling me it's fixed. Last week the inevitable happened so the vehicle was again towed to Audi Centre Northcliff after discussion with Audi Customer Care wherein I expressed my disbelief that Audi Northcliff knew how to fix the problem. Audi Customer Care advised me that since Northcliff had the vehicles history, it was the best place to take it. It's still there.