[Hayir]

OP stated that BMW couldn`t identified the reason they never had told him that it is not their fault.

Think you car is broken under warranty you take it to dealer, they tell you that they can`t identify the problem and they refuse to repair under warranty. What would you say?

If they are refusing to pay under warranty they need to give some reason. In this case Bmw at least owes an answer to the OP. With this logic BMW could simply avoid all the warranty claims, they can say they couldn`t find a proof showing that it is manufacturer defect.