I have had the same issue since day one. So now I just leave a rolled up towel across the whole bay below the door so water will not travel further than the towel, unless we get a real bad downpour.
I am thinking its coming from somewhere higher that the top of the door, because the carpet on the wall next to the door feels damp at times.
Both doors (on each side of RV) were resealed at the factory and extra gasket was installed on the street side doors (since they are side hinged) - that one seems to be a lot better, but the curb side has never been fixed...
I guess one day I need to unload the storage area and either wait for a good rain or hose if down and see where water might be coming from..
Good Luck - We both will need it...
2015 F350 DRW, 2015 Sequoia SQ38HRL, G614's, Titan Disk Brakes, Trail-Air Flex Air pin box, SRE4000 w/ X-brace, Heavy Duty Shackle Straps w/ Wet Bolts & New Springs.. Now I am done for awhile.