The issue with this problem is the absence of outer door seals. You will find that after driving in the rain that there is quite a 'tide mark' of muck inside the door sills where the spray is forced in along the lower door edge. Once in it does not easily drain out. Therefore the water tight integrity is relying on the one and only door seal which is very easily damaged by scrapes or compromised by other muck getting trapped between the door seal and the door opening seal. The B pillar is particularly vulnerable. Moral of the story, have these seals renewed at every service or risk having the inside smell like a swamp !