Rainwater is finding its way into the ventilation fan situated in the
passenger footwell.

Is this a known issue?

I am guessing that rainwater is being sucked from the rainwater drainage
channel below the windscreen motors.  I have cleaned the channel and the
drainage holes seem clear.

I also think that the water collects in the air ducts supplying the heat
exchanger.  When I corner sharply the water flows along the airduct and hits
the fan blades and makes a 'swishing' noise.

Are there any modifications I can make to stop this happening.