As far as I know there is no sensible limit to the number of posts per topic.
Realistically, until somebody discovers and posts a solution to the problem all one can do is add "me too" posts to increase the weight of evidence against Audi, and therefore is worthwhile even if there is no response.
It seems to me, as somebody who is unaffected by the problem, that Audi, as the vendor of the affected equipment, has responsibilty for its faults no matter which subcontractor made the radio for them. That is my interpretation of the Sale Of Goods Act 1979, and its successor the Consumer Rights Act 2015.