Those loose plastic trim strips around the perimeter of the windows are not part of the seal.? If that was the only issue you would just put a little caulk underneath them and restick them down.? Caulk doesn't stick to that plastic well though, and that's why they come loose.? That plastic is there to prevent UV from degrading the adhesive that hold the window itself to the trailer.
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If you took off the windows and vents you could get at a lot of the delamination from the window edge.? You could push epoxy way up into the delam area with a stick or tube without drilling holes.??
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It's just a matter of whether you want to do all work.
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