I have a wagon and have solved different issues with the back door including a broken handle. It seems your door lock is locked preventing from closing.. Check the electrical connection and make sure it is operating. It can be tricky. mine was not working for a while and out of the blue started working. if you go into the door mechanism and find a loose rod I devised a simple fix it for the problem of broken plastic connectors. I have solved it joining the rod to its location with one or two short zip ties on each end through the metal hole that used to house the plastic connector. They work better than the original to solve this problem which happens often on the driver's door on 850's with high use .