Just discovered that the sealant around my tail light was not sticking to the fiberglass and decided to remove the tail light assy and check things out. Apparently the factory failed to put sufficient butyl tape behind the light and it has been leaking. The wood around the hole is soft and crumbly down at least two inches or at least as far asI can test with my finger. I removed the other tail light to check it out and found ample butyl putty behind the light and no leak.The dealer had sealed everything with silicone when I bought it but silicone does not stick permanently to fiberglass and aluminum. So it apparenty got by the silicone, and with little butyl behind the light water entered the hole.
I will now start using Geocel Proflex RV sealant to caulk all of my seams and joints. Silicone is not the proper thing to use. Everyone better pull their tail lights if they suspect a crack in the caulk!! My last 5th wheel (Fleetwood Wilderness) had a leaky tail light that rotted the entire back corner of the camper and part of the floor over a period of the 7 years I owned it.
This maybe an old topic, but this brought out many things for me. On the issue of tail light leaks, I think that you might change up some of that for a good brand like what sir michaels and other brands would give to you. I'm sure by now things are now well in this one.