I had the left rear window out when my motor was stuck in that position. I think it would be harder and maybe impossible (?) in the upper position.
Didn't open the motor. I just sprayed some WD-40 here and there and it started working. Greased up the wire and put it back in. I had to run it all the way down to get the glass back on.
Maybe you can get the white guide/tab off the window motor assembly and then be able to remove it. I am sure there has to be a way...
Sorry I can't be of more help