Owned a 2004 Winnebago that had the roof ready to lift up for about an 8' length from the front on both sides. Shop found it and repaired it. Not cheap. We always did annual inspections and recaulking as needed.
Two Friends both have Winnies and have had the same SAME ISSUE! One has had repeated water leaks coming down the interior wall(roof pulled away vertically over the front passenger window) ) and the other had the roof begin to peel up along the side as in the picture posted above. Both needed major repairs - water damage owner is a fanatic about maintenance and re-caulking, the roof peeling one was oblivious, not a good thing! They were very close to losing a large chunk of their roof.
The J channel design has been well reported as having issues. Loved my Winnie but the roof design became a source of major concern and significant expense. I cannot get on top and do maintenance but annual inspections are a must regardless of manufacturer. Don't forget windows and slide seals..........
Some here may have been very lucky to not encounter this issue. Check the owners forums for more information. May no one here ever encounter this issue.