I will be guessing at this
At bottom of your window opening, where you might rest your elbow sometimes as you drive, there is a Felt channel that does 2 things, it helps the window glass to keep from moving side to side & to help keep rain from going down into the door.
The other thing is a bit more involved
Watch a Youtube video on how remove the inner door panel off of the door.
Once that panel is off, there is a 2nd panel
Look for a rubber access panel, it will be about the size of palm of a large hand, it will be squared off & have a short rubber tether. When you open that panel & let that part hang down.
You ought to see the corner of the window frame & glass
If i recall correctly, you will see a white plastic thing that sort of holds the bottom of the window from moving while driving
This may help you , i just googled it
2016 Ram Truck owners are complaining that in cold weather, their truck windows are falling off the tracks and down into their doors.
www.torquenews.com