I had this problem and found a thread titled 'Door window drops but immediately jumps back up'. Search for it.
It identifies the problem as a microswitch inside the door lock assembly. I don't think you can get the switch by itself, so I tried lubricating it as recommended (no luck) and then replaced the door lock assembly. It was a DIY for me.
The part is called the 'Door Lock Mechanism', and is available at:
http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search.cgi?command=show_part_page&please_wait=N&make=POR&model=986M§ion=INTpnl&page=1&bookmark=7&part_number=8N1-837-015-C-M100
You will need a special type of wrench called '12 point triple square' to remove the part from your door, but I found a set at the local O'Reilly Auto for not much $. It is used to remove the 2 bolts visible on the door jamb part of the door.
Good luck with the repair!
