Cuda and Challenger are the same, no issues there. So lets try and establish some clearer lines of communication because I am slightly lost.
So if I understand you, when you move the window from side to side (like you are facing the front of the car and moving the glass towards the inside of the car and toward the outside of the car), you are saying that you can see the glass move on the plastic guides? Do you have the window guides in? The window rides against them to a degree but they do limit the "in and out" movement and if installed correctly would not allow the window to move inward.