This article is from the Chrysler-Plymouth-Dodge FAQ, by Dr. David Zatz with numerous contributions by others.
Mike Stallcup couldn't get his minivan door to close, so he turned the
power locks on and off a few times. Fixed it.
Someone else found the problem to be a loose trim panel held to the back of
the door. The roller on the track at the top/inside of the door was also
out of alignment; the bolts had loosened and the door was not closing
tight. Check the tightness of the bolts.