Surely it has to be the seals. I can't see how you would get water ingress into the interior without the seals being shot. Does it happen on both sides?
Yes, and its not the interior, just where the kick plates are. My car is parked on a steep inclide. Today after being parked on the flat in the rain for a couple of hours...no water....
+1 never happens on the flat, possibly why Nissan never found the fault & claim its normal