I have this problem on my wife's 2017 Audi A3 hatchback on the passenger side front and back. What a nightmare. I put a wire hanger through what I thought was the drain lines from the engine bay, but it didn't seem blocked.
Thanks guys ! If i can add another tips, there are also 2 water drain like this under the rear wheel mud guard, they are located behind the wheels Another 2 drains flow is come out bottom the car in front on 2 side, just under passenger and driver seats, just put a verry thin screwdriver or something can fit in the small hole of the hose and let the water out.
I been searching for a longtime and spent a few thousand dollars on this problem on my Touareg. A big thank you for where to look for the drains! VW never tells you much but loves to take your money! Thanks