if there was a problem with the safety switch I believe that your window wouldn't move at all. however with the window up you can get to it from the inside. if you want a permanent fix, take the tailgate cover off the inside. with a flash light if you can try to look up and locate the white plastic saftey switch near the release handle.. there are a couple of wires that run up in the middle of the tailgate. I believe the two for the switch are the only ones that run up on the very inside of the tailagte infront of the glass up to where the handle mechanisms are. All other wires run on the outside of the glass to the window motor. Once you find those wires, in an open easy to get to area ( incase you ***** up or change your mind someday) cut the two wires, strip and twist them together and seal them with either shrink wrap or electrical tape.
make sure they will not be in the way of the glass and test your window. if it was causing you problems they should be resolved.
now your window will move whenever you want it to. jusg be sure your tailgate is fully closed before raising it otherwise you run the risk of cracking or shattering your rear window.