@En4n wow that seems like a really good idea to be fair! I'm pleased to see this post is helping others who have experienced similar issues. Awful design flaw for certain!
Shockingly, around 18 months since my issue with this and I'm having to send it back to Audi next week as I experienced this issue again where I noticed a damp smell in my car, this time on my drivers side as we experienced heavy rain in UK last couple of weeks - that said, luckily, it did dry itself out this time as I left my roof down all day when it was really hot last Friday and it's dried itself up; and as it's been less than 2 years since Audi Watford repaired it for £960.00, it's still under manufacturer warranty so they'll investigate again free of charge. I also make sure I send my car to Audi Hatfield now rather than Audi Watford; Audi Watford are very untrustworthy and have lost me as a customer and the service I've received since I've been going to Audi Hatifled is far more pleasant. If costs are of concern Audi do offer a thing called Bumper.com which is basically Klarna for pricy car repairs at 0% - For specialist jobs like this, If one can't resolve themselves I'd take it to Audi directly as you get warranty if anything goes wrong and can hold them accountable.