How do i get to the window track on a 1993 buick Century?

My girlfriend has an old '93 century and the back passenger side window loose, when the window is in the down position it swings back and forth, I started to get the door panel off but i saw that there is a second sheet of metal over where the window motor is, is there a way to tighten the window track or am I going to have to change something out? The window still goes up and down so i know its not the motor or the regulator, wat else could it be?How do i get to the window track on a 1993 buick Century?Guess they can be tightened some use 10mm bolts other are riveted.