A properly sealed window will not let water pass. The gutters sound like a good idea. I guess they work by diverting water from the window.Here's where I go for caulk and sealantshttps://delamrepair.com/sealingproducts.html
I would look at the perimeter window sealant very closely. Pin pointing a water leak can be tricky. And once water gets into the wall deamination can happen quickly. I have had a good experience with www.delamrepair.com in dealing with sealing, caulk...
If it's a composite bonded wall then it should be solid. Some rear walls are of a 'floating" design and have some give. However it would be uncommon to have a large window on this type of wall.
RLS7201 wrote:The RV industry has punished us with Dicor calk for years. It was/is never a permanent solution. As previously noted, over time it needs to be removed and reapplied, due to cracking and unbonding.A more permanent solution is Sikaflex 71...
