I wanted to offer feedback to all of you that I received from a customer this week, he offered an explanation for the water ingress of IP67 rated antennas from his experience...
I have a background in seismic exploration equipment - lots of field experience. We once had equipment deployed in Texas which would fill with water no matter what we did and the problem was everything we worked on for months. Ultimately we build cases from custom aluminum extrusion with machined grooves for O-rings and 3/8 inch plate aluminum against the O-rings. Not enough - water would still collect inside.
In the end, I defined a concept that I call "Vapour Pumping". Our cases had considerable volume inside and this is probably the basic problem with your antennas as well. During the night, humidity rises as the air cools. The lower temperature creates a vacuum in your case which no IP rated case with internal volume can deal with and air ingresses - not water. This high humidity air brought water with it which then condenses on the inside of the case as the outside air continues to cool.
In the morning, the heat comes up and the case releases the excess air that entered in the night, but the water remains in the case. Repeat for a week or so and you now have "mystery water" in the case. It did not fail it's IP67 rating, but it also is full of water.
Outdoor LED lamps same thing. What needs to be done is minimize the internal volume of the case.
I hope that insight might help.