UKPassats

Has anyone had problems with condensation in estate rear lights? My original lights had a problem so I bought some brand new ones from VW and after around 5 months they are doing exactly the same thing all the nuts on the back are nice and tight i've checked the seal and everything seems to be in order, carpets aren't damp, neither is anything at the back end just inside the lights I'm going to try some small silica gel sachets anyone got any other ideas?