Brand new million rand vehicle defective

in June 2015 I purchased two new BMW's valuing more than 1.5million Rand. The 2015 550i GT almost immediately started to have an intermittent knocking noise from the rear of the vehicle. I took the car to my nearest dealership who believed it came from the welded joints made during the manufacturing process and attended to the problem including removing and refitting the sun roof. The problem continued. Club Motors collected the vehicle and had it for 3 weeks and returned it to me with the same problem. I was asked to bring it in again and during the test drive the problem was recognized again. A few adjustments were made and during the trip back home, the problem presented itself again. BMW SA were continuously included in the communication. BMW suggested the Technical Area Manager check the vehicle but because I could not fit into his schedule for when he visited the dealership I was advised that he will only be able to see me in October 2015. I have personally spent millions on BMW's in my lifetime and the service and seriousness of my problem is completely being ignored. No attempt is made to accommodate me. I drive to the dealership, I wait for a technician this for a 1m car.