How do the seals look? Are there any gaps in them? Are they dried and cracked? If so, you should be able to replace them. Try looking on Amazon, or Camping World or any other rv supply store. Theses seals need to be conditioned with a rubber conditioner occasioanlly to keep them pliable.
I also saw on another forum some people have had to add silicone to the outside top of their cargo doors because the factory missed a spot. This solved their leaking issue.
Steve & Sue
2017 Grand Design 297RSTS Travel Trailer
2017 Ford F-350 Lariat Crew Cab diesel 6.7 SW LB 11,500 lb GVWR package
Former: Crossroads ST26RB