I'm thinking it was more than likely causing by you or the previous owner putting the window down when it was dirty. I believe that is the case because mine is the same way. Don't know why it is close to the door frame on both sides though.

1996 MM Zetec, ATX 192000 kms...not dead, but I'm not fixing it White people love Wayne Brady because he makes Bryant Gumbel look like Malcolm X.