I am having similar problems with my newly-purchased 2003. The wetness shows up in the top storage well behind the seats, and migrates into the trunk, causing condensation. No trouble in the footwells. I have seen trails of water from the joint between body and cloth top... does this mean my drains are clogged? Did they ever fix it satisfactorily?
In my experiences of owning the Audi TTs I have never had a problem; I had even bought some that were "Salvaged" and fixed them up to be a great car.
Personal input is I think everyone has had their own experiences. Whether it was good or bad.
Normally I use a mechanic who is not from a dealer. Dealerships just want to rip you off.
I would go out and buy a new top, leave everyone out of it and use it as a tax write off. A lawsuit against Audi would not be worth it, you would spend more money in court costs, than to replace it yourself.
Audi TT Roadsters have an obvious design flaw with the drain system for the convertible roof. The drain tubes are flimsy plastic tubes lined with foam and a spring. This design means that anything that gets into the tube (that isn't water) will ultimately cause a blockage. That means the tubes back up and flood into the B pillar causing electrical failures in the car.
After my local dealer used an airgun to "blow" the tube clean I discovered that they had actually blown the tubes off. This was only discovered with a video inspection camera.
Even after having the tubes replaced and the car dried, I am still suffering electrical failures and will ultimately get rid of this car.
Same issue. 2004 Audi TT and the water does not drain properly, backing up into the car.
In the past year, I have had the battery replaced once and the central locking unit/convenience control module replaced twice. This has happened a third time and rather than replace the unit, I am replacing the car.
What "engineer" designed a system that would allow water to backup and get into the electrical system? Despite this design flaw, the dealer says that it is my fault, not theirs. I guess I designed the car. It seems to be a problem for this car for all years.
"I would go out and buy a new top, leave everyone out of it and use it as a tax write off."
Exactly how would you justify a new top for your convertible as a tax write-off? This IRS agent would like to know...