Hi George,
Where in the basement are you seeing the water? By that, I mean, is it behind the bulkhead wall under the kitchen or in the main storage area or in the front section that drops down?
If it's in the front most section, check the rubber seal on the split door and make sure the cams are turned the right way on both locks to ensure a good snuggly sealed door when locked.
Sounds like you resealed around the frames of the storage doors so that's covered. Consider getting up on the roof and check the the seams forward of the kitchen. The seams where the roof membrane is attached at the edges of the trailer. Look for seal voids. The seal where the front cap is attached to the trailer, across the top and down the sides.
I searched a bit but didn't find where it's been into a dealer for this yet. If you find nothing further, consider getting it in to a dealer.
Best of luck,
Jim