Nissan sold us a car with an auto start fault, now they reject warranty claim

Four years of reporting a fault to Nissan without proper help, records available at dealerships but now my warranty claim is rejected! In Jan 2019, Feb 2020,Jan 2021 and May 2022, we reported to Nissan that the car had an auto start fault. All these years, they look at it and in no time the same fault reappears. Suddenly, this has now led to other issues and nissan is declining the *** after logging a complaint, they had not yet even called the dealerships to get the job cards to see the truthfulness of our claim. Now i realise, the ombudsman and social platforms are probably the only way to get help because I dont have a car. A faulty car that was sold by nissan and they failed yo fix