I had the same issue. It will likely be a blocked sunroof drain. Underneath the car right by the wheel arch and in line with the front of the door is a tiny hole to allow water from roof and windscreen to drain. It could be blocked. I used a very think cable tie to unblock
RX400h - Damp Footwell - passenger side
in RX 300 / RX 350 / RX 400h / RX 200t / RX 450h Club
Posted
I had the same issue. It will likely be a blocked sunroof drain. Underneath the car right by the wheel arch and in line with the front of the door is a tiny hole to allow water from roof and windscreen to drain. It could be blocked. I used a very think cable tie to unblock