Leased A Lemon Audi A6?

Hi all,
I need some advice; because what has happened to me is really beyond my belief.
Two years ago, I leased an Audi Quattro A6. The care handles smooth and
I love it. Except, every month and sometimes twice a month, I have to take it to the dealer because of a sensor light turning on, brakes not working, radio shutting on and off, steering stiff, recall of coils, et cetera. I have counted about 17 visits to Audi in the last two years I have had the car.
I wrote a letter to Audi in the US; no response. I wrote another one with certified mail and return receipt; they received it and no response. I then wrote to Audi in Germany, to which I received a reply that their US offices handle US complaints. Till this day, they (US office) have not acknowledged my letters.
In the letters I told them that I have leased a lemon. How can a quality German car like Audi have so many problems??? You would think that even a letter of apology would be produced by them? Nothing!
How am I suppose to want another Audi when I have received no response despite my letters?
Have other people here had these problems? The dealership has been excellent in providing service, lending loaners, et cetera, but tell me they just sell/lease and service cars they receive from Audi.
I love the car (when it's running appropriately,) but I can not consider leasing or buying one again. I'm considering Jaguars or Lexus after I do my homework.
I really appreciate any advice regarding the aforementioned.
This is my first (and perhaps my last) experience with a German vehicle. I respect German machinery, cars, et cetera very much, so I can't explain what has happened?
Thanks in advance,
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