My a/c covers disintergrated when I tried to repair, turns out they were plastic not fiberglass and the sun made them very brittle. On line found a supplier in Canada and they shipped for about 100 each, they were thinner than the originals but company did say they warrantied for life, whatever that means anymore.
Looking at mine without the covers, lots of places for water to get in. All seams covered probably need to be uncovered to find a leak. When I replace my vent cover in the bathroom found a rusty screw under the caulk, never would have noticed it otherwise, water never did drip into the rv, amount getting past screw must have been minimal.