I just remembered that when I got the T-Cross for a test drive from my dealer a month ago, the front lights had water inside, almost the same as your rear lights. I think VW has an issue with the sealing
My R line is suffering with the same problem, to a somewhat lesser degree. I had condensation in both rear light clusters, just before Christmas. The car was garaged for 2 weeks whilst we were away, over Christmas/New Year and the vast majority of the condensation has disappeared. However, have now taken car out of garage and will see if the condensation/water ingress comes back.
Dealer has been informed of problem and has asked to kept up to date on this. Will post again, as and when it manifests itself!
My lights were changed yesterday. Went couple weeks ago to show water in the lights. They took just photos and said that they need to ask vw before anything. After few days call came and they said that new rearlight units were ordered from germany and i made reservation to shop again. Now both unit are new. Hopefully these wont leak