Understand. As others have mentioned, the SO-239 isn't sealed like the N connector. And no matter good a job you think you did with weatherproofing, it is still very vulnerable to water. In my opinion, if a UHF antenna has an SO-239 it is crap. I would be curious to as what you find when you pull it down and inspect. Good luck with it.
Oh, and I never did find out what antenna you're using. It's possible the antenna radome is compromised.