Tail Light Switch problems of the 2014 GMC Acadia

Two separate warranty claims. Dealer did replace all tail light assemblies- once on normal warranty claim, the second incident (lhs only) on customer satisfaction basis. Issue> rear tail light lens clouds up with condensation / water to the point that stop light visibility is affected. Approx 50% of the lens is covered internally with water droplets and condensation potentially violating fmvss safety standard for visibility. Apparently the lamp assembly is not sealed and permits water intrusion. Condensation does not clear up adequately- in my case after 16 miles of driving or leaving the SUV outside overnight. Response from dealer: gm issued a letter stating warranty claims will not be honored for water condensation on tail light lens.