I had a similar situation on my previous trailer. A small leak on the front left side of the trailer. I pulled the caulking off the screw heads and they were rusted. That means water is getting in. I pulled all the caulking off the retainer bar and removed all the screws. I was then able to pull up the edge of the front wrap around and see the damp wood. Nothing was rotted beyond a small section that only went a centimeter deep. I cleaned all that out, propped it so it stayed open for a couple of days, and let it dry out. I put the whole back together with new screws and covered it with Eternabond tape. No more leak. And when I traded the trailer the dealer didn't bat an eyelash.
