The roof inspection might help reveal a bit of answers. I found a refrig vent cover was not healthy in my rig and it was a cause of my obscure leakage. I replaced with a generic CAMCO type cover for my Dometic install and furnace type leakage disappeared. Have you topped your rig yet for a peek?
1994 Fleetwood 33H
1995 Fleetwood 30H (parts vehicle)