I've found this will get damp from washing your car, especially when using a pressure washer.
I'm going to look at how this hangs down from the two mounting points, because I think it's sitting in between the rubber, protruding out from the rubber and getting wet. Either that, or the seals are crap.
Solution for now is to raise the trunk and let it dry out for a bit, after washing the car.
Love the concept, honestly looks like it will get pinched by the gasket every time it closes though. I would think that installing on the other side of the latch would rectify the issue.