Originally Posted by Iggy
Considering it is a 2004 I would suspect the wood may have become water soaked and dry rot has set in.
How does it look inside? Does it also sag 5/8"?
My money is on water intrusion as well.
Find and fix the leak. (The leak most likely will NOT be where the sag is)
I would look along the exterior wall seam. The water will then travel to a low spot (the center of the slide span is a logical place for that to be) and settle there. Once softened the sag gets worse.
Then look and see how bad it is after it dries out a while (put some heat in the camper to help).
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