Refuelling with 3.0TDI year 2008 almost impossible

Hello, my father bought a 3l Tdi Bj 2008 GP1,5 as a leasing returner 3 years ago. A big problem with the car is the refueling. Regardless of the tank column it is impossible to snap in the tap and let the tank run full. Filling is interrupted again and again as if the tank was full.. A tanking with empty tank takes about 30min and is always a torture.. Since the car is to be sold now, we have to take the problem again. Shortly after the purchase the complete ventilation unit of the tank has been renewed for a repair sum of about 200€. But this without success.. The friendly does not know any further, the plant speaks of the individual case. A next step would be the exchange of the complete tank for 1000€ including working hours but without guarantee on remedy. My question is now whether someone knows this problem or has already heard of it. The works very gladly speak of “individual cases”. Thanks in advance and many greetings!