If this is a new, less than a year old TT, check/inspect all inside walls where you know there was not any sealant!! The first bubble in the inside wall go to the dealer for a wall replacement!!
I had a competitive TT, they did not seal the rear window, it leaked. The rear inside wall bubbled and separated from the insulation. The whole rear panel (inside/outside walls) had to be replaced. The outside looks OK. The inside was done in a hurry, unfinished trim, shelves crooked, etc.. The dealer and I are still having words.