2000 SEL power door leaks during rain?

Has anyone else had this problem? We have a 2000 Windstar SEL with dual power doors. The driver's rear door leaks horribly when it rains. The door doesn't seem to be totally flush with the side of the van, yet it isn't open enough to activate the door-open sensor.

Is this something we can fix ourselves or is this a known problem?

Thank you,
Tracey in GA