ARX450B

I recently purchased a new Cushcraft ARX450B . I am using it for a scanner antenna. It works great, but when it rains I can’t pick up the 450 band. It will start to pick up VHF High channels. This is the strangest thing that I have seen before. The sun comes out and I will start to receive the 450 band and loose VHF High again. I have been up on my tower checking and making sure all connections are moisture free. Any help on this would be greatly appreciated.

Thank You