Condensation Behind Tail Light

I have a Leer 100XR and it's a little over three years old. I noticed water seeping through the hole where the third brake light wires run and noticed my light had condensation behind it. I ordered a replacement off eBay and when I got the new light in I ran a bead of silicone around the harness and along the top of the new lamp. The replacement also had 3m tape on the bottom as the factory one did.

Not even a month later and my brake light is full of moisture again. What gives? I've at least eliminated the issue with water getting into the cap but apparently the lens isn't 100% water tight and all these humid summer days have found a way to make a brand new lamp look like crap. I plan to run silicone around the rest of the lamp if it ever dries out but I hate making it a huge pain to pull that light off if the need arises. Anyone else encountering these issues?

 

yes.
I disassembled my light.
Cleaned rust off some metal bits. Dried it all with heat gun. Reassembled with RTV sealant. Even sealed around wires at the light. Still some moisture in it somehow and I warped it with too much heat gun use.

I just ignore it. Tempted to make my own light but it likely would not fit the lines of the shell as well.