Has the unit had a Seal Tec machine (duct blower) used to find the point of the leak? If not I think if no one has been able to find the leak this is a good place to start. It may just need to have the room adjusted to close tighter in order to seal properly when closed. Good luck and keep us posted.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7