Assume you have a diesel?
I looked it up as well before I posted and the problem is 95% of the people on the forum have gas / petrol cars, not diesel. Diesels aren't sold in the US on any Audi until very recently. Hence the lack of info. But, as I said, anyone that posts an electrical issue after a big rain, my thinking first goes to water being where it shouldn't. Solve that, and then see if the mount issue is still there. Some of these electrical issues "fix themselves" when you solve the water intrusion issue.
13 S5 Manual
03 1.8t sport Quattro with 115K
02 sport quattro with 205K; (killed by a 4x4)