Recent threads here have referred to the issue of clearance lights' lens deterioration. The front ones on my coach are displaying such failure this summer, after only 5 years of age. The ones on our old '84 Pace Arrow never cracked like these, and the lenses (or bulbs) were easily replaced. As you've seen, you have to replace the entire fixture on our coaches. Mine don't leak yet, but eventually will. Even with a good seal, rain water and condensing vapor can get inside the micro-cracked lenses and into the coach via the wire port. Water can accumulate in a low spot in the overhead, then run down when the coach is parked at just the right angle.
I reckon you are looking at cutting silicone again, Frank. Consider resealing with Lexel instead of silicone. It would be nice to have longer-lasting LCD lamps in such fixtures, esp. if you can't just pop a lens off to replace a lamp or lens, so you might check into that. I've just started regularly applying Aerospace 303 protectant on the lenses to see if that helps ward off UV deterioration, but it's too late for my front ones that are pointed south while parked at home. A better plastic is needed in this application.
Joel