Sorry to hear that.
I only had an issue with a 120 lens, where the autofocus did not work at all (i.e., the autofocus did not react at all when the shutter was pressed). My dealer contacted Leica which within a couple of days shipped a new lens to me while mine was still on the way back to the dealer. Otherwise no issues (fingers crossed).
Good luck with your letter (I think if I had written it the language would have been much harsher).