We had trailer once that one light was so water tight that condensation built up. I unfolded a paper clip, held it with a vice grip pliers and heated on stove then melted a small oblong hole in the plastic creating a little tiny vent.
Wish I could of taken credit for the idea, but can't. Was before I retired, on my delivery route was Pacar (parent company for Peterbilt and Kenworth) That's what they did when some came out of mold wrong way and did vent right.