[Mikendebbie]

My unit does not have the window behind the sink.
For the first 3 years we owned the rig - the little black clips were holding the vent flap closed - but I did not know they were there to use. We still used the exhaust fan and I don't think we noticed it was or was not working correctly...and then one day I was shootin' at some food...just kidding - I was washing the rig and discovered the black tabs. I decided to leave them open. The vent flaps a lot in wind and makes noise - but we have not had any leaks.

For those of you with the window behind the sink - have you checked that back wall under the sink to look for water damage on the sidewall? My first suspect would be the window. As someone stated above - silicone the top of the frame and around the sides a bit - then see if the leak continues.