I’m guessing this post is about a 500? While in a dealer we used to see lots of them with wet footwells and they also suffer from poor sealing on the floors which means any amount of water sprayed over the car does nothing. When it comes in through the floors it’s after driving in the rain. They can be a real headache to fix. If it’s not the screen remove the seats and carpet and spray all of the outside and underside with water. I sometimes poured water in the footwells and then checked seams underneath for missed/faulty sealant