My 04 had the exact same delamination issue. It started to appear under the cabover, then ran down the firewall into the basement and out at the rear dump valves.
It can be repaired correctly and might be cheaper than trashing the camper. After the repair is made , Eternabond tape will help on the roof seam and a good caulking on the clearance lights will do the job once things get dried out. That's the key, you have to get things dry to prevent a mold issue which can be deleterious.
After AF tried to repair it 3x, I had a dealer strip it down and repair it .
In my case, after stripping the entire cabover , the dealer found where the leak originated by the factory cutting too deep (looked like a bad off the mark router cut) at the cabover curve (near the pass. side clearance light) . That, in conjunction with the bad roof seam was my problem.
What happened:
AF (someone at the factory original build) discovered the off mark router cut it and said ooops . Instead of replacing the labor costly filon sheet they opted to fill it with caulk to slow down the potential leak/delamination, hoping to escape thru the 2 yr. warranty period.
The caulk job only lasted 11 months and that's when it showed major cabover delamination. The only way to really fix it was to replace the filon which AF eventually agreed to do at the dealership.
The fix :
This is how it was explained to me by the dealer who had made many successful cabover delam repairs on these units. After seeing my TC all apart, I could now see how it happened .
AS Kerry stated , in older units , the roof seam build layering system that AF used back them was an issue . (btw, its not just a wood framed camper issue . I saw a few tc owners that had the same issues with the alum framed models in the 2005/2006 generation. AF eventually did something about it )
If you notice the slope of the cabover roof, the water runs to the front roof seam (when the camper is parked), it should be layered like a shingled roof to shed water and allow it to run off the front of the cabover .....but it isn't layered that way. The campers roof layers are layered in the opposite direction allowing water penetration after multiple continuous soakings . A pin hole in the roof caulk would allow water to penetrate the ends of the filon. When brought to the attention of AF they claimed it was built that way to shed water when you are driving.
Well, that's all well and good but TC's spend most of there life parked not moving and that allowed water to sit puddled on that seam and eventually soak into the ends of the filon where the filon ends are exposed and NOT encapsulated, they should be sealed and that's what this dealer did in his repair, he sealed the filon ends as he relayered the roof in the opposite direction.
Because of the cardboard like backing ( the backing allows the filon to bend) , it soaked up water like a sponge. The water would then gravitate to the lowest point (like getting trapped under the cabover) and eventually down into the basement then onto the ground.
After the tc was repaired it was dry as a bone and never leaked again and I never resealed it or ever touched it other than to clean it.
I think a lot of changes were made and people replaced and the product stands in better light today.