Quick update... Just spent the last week working on this mess... The entire 5th wheel section WAS soaked and has suffered a bit of damage. I looked and looked and looked some more, but could find NO hole, leak, gap, whatever in the roof. Finally, I gave up and proceeded to clean out the gutters. Then, I found the hole. It was just at the tip of the rain gutter where it started to slope downward at the front. it was maybe an inch and a half long.
It wasn't a big hole, but it MUST have been the culprit. Since the weather was all sorts of nasty and cold, and a storm was coming. I ran down to the local RV place, got a hunk of butyl tape, and plugged that hole as far as I could stuff it. As far as I was concerned, the hole was plugged, and we wrestled a tarp over it in 20 mph wind.
Lucky for us, the tarp held for a week or so. (We had to leave the seasonal and head back home.) Got a call saying the tarp blew off, but all looked well, so we took our time getting back.
Much to my surprise, once we got back (about 2 weeks later), the camper was DRY. Yes, there is quite a bit of damage, but there is no more wet. There is also precious little signs of mold.
Total damage assessment looks like just the 5th wheel section is compromised, and we got it early on. Floors are good, walls are not. I will add photos when my supposed smart phone decides to be smart enough to cooperate.
TL;DR: Moral of this story is it isn't always the roof, and if you're permanently mounted in a seasonal, CLEAN THE DAGGONE GUTTERS!!!!