Hi im new member, had my Audi A6 Avant a month only 3 year old. Done 16k. I've noticed the driver's side door seems to collect water on the sill where the s line runner goes across and it's also sits on the seal that goes along the bottom. None of the other doors do this. Just worried that in winter this freeze and jams door etc. Any advice or ideas what might be causing this would be much appreciated. I'll try attach a pic of drivers side and passenger side in comparison. Thanks 

Hello, I had a Audi a6  and the passengers foot well filled with water and ruined the control units. This was due to the vents becoming blocked  under the bonnet . Also the battery box was above the footwell and this I sealed with mastic used on fish tanks. The floor mats took an age to dry even when using a dehumidify. Hope this is not your problem.