Lots of possibilities. Contacting Forest River might be helpful but might take a while to get a reply. If the goop has lost integrity as it appears the windows might be at risk. I'll assume (dangerous I know) that he goop oozes more in the summer months when it's hot out. You might gently push from the inside out to see if the windows are loose at all.
One of our members Hap Hazard, and many others, have had good experiences with Jim at VIP RV Service,
www.viprvservice.net I'd call him and see if he can assist you. He might be able to help just via the photos and save a haul into the shop.