If your roof is ok then the suspect is the window. First try looking at each inch of the seal for the tiniest gap. Use your fingernail and pick gently at the seal to make sure it is attached to the wall and the frame. Even the smallest lack of a perfect seal can leak. As you drive the simple motion can open the seal or form a vacuum than will suck in water.
Most agree that Dicor is the product to reseal the window, avoid silicone products.
A second method is to go around the window with a strong flashlight and have someone on the other side to look for light coming through indicating a gap.
Jayco missed a quarter inch long patch on one corner of my front window. I ended up checking every other window and door. Only bad place I found.
2017 SLX 195RB
2014 Jeep Grand Cherokee Overland, gas 3.7 V6
Andersen WDH hitch
Dometic Milenco Aero mirrors