Stellantis Opel Crossland 1.2T Engine Fault Requires Replacement Despite Low Mileage

I’ll share my Opel journey. I purchased a 2021 model with license plate 34 DZT *** second-hand 1.5 years ago, trusting Opel's renowned quality. After all, it's German. Or as much German as Renault is Turkish. A few months after the purchase, the car's warning light came on. Since there wasn’t an Opel service center in my city, I had to travel to another city. They cleared the error and sent me off, only for the light to come back on during the return trip. After a second visit with the same outcome, a service center finally opened in my city, and I reported the issue. During this process, I discovered that the engine's top cover set, knock sensor, and other parts had already been replaced previously. The local service center collaborated with headquarters to identify the problem. They replaced the knock sensor—didn’t work; replaced the coil—didn’t work; replaced the spark plugs—still didn’t work. Since the error occurred in cold weather, the car stayed at the service center for 4-5 days. Eventually, they inserted a camera into the piston heads and found carbon buildup. Despite a previous top cover replacement, the problem hadn’t been fixed, and now they claimed the entire engine needed replacing. However, they couldn’t provide a satisfactory explanation for why this was necessary or the cause of the issue. No matter how many complaints I filed, there was no positive outcome. I ended up researching the issue myself and learned a lot—almost enough to become a mechanic. My findings led me to a YouTube channel by 'Salihli Uzman Oto', where a mechanic claimed this was a factory defect in the 1.2 PureTech engine. He had identified the issue after extensive research and fixed it without replacing the engine, with vehicles coming to him from across Turkey. However, he charges exorbitant prices and doesn’t reveal his exact methods. Thanks to the Stellantis Group, mechanics like him have likely become millionaires. During this time, I discovered countless similar complaints online, all with the same outcome. Owners of cars out of warranty are left stranded. This issue even occurs in cars with just 10,000-15,000 km. How does a car's engine reach the point of needing replacement within such low mileage? Why can’t service centers resolve this issue and instead insist on engine replacement?