. The water would run into the gap between the wall and floor and makes its way to the step well. I am not sure if I have it all figured out yet just waiting for another heavy rain to see if it does it again. Hope this helps.
Yep! Mine was coming in from behind the trim covering the wall and lower trim panel, between the coach door and the passenger door. It would run across the floor into the well, and manifested itself by a rust drool from the bottom left of the door frame between the door frame and wall. Found it when i was washing the camper, wondering where the water flowing down the wall was going. Just didnt seem to be enough dripping down!
It was difficult to find because there was a long delay from when the water entered and when you actually saw it in the stepwell. When i first did the 'hose test' it didnt show. The time required to scrub the roof and sides revealed it. I took off the trim, sealed behind and reinstalled.... never leaked again.

Also had the water collecting on the shelf in the undersink cabinet in the bath from the outside shower unit not being sealed. Solved.
I use the brown 'butcher paper' as a tattletale for leaks. I put a layer on the bottom of the stepwell, then put the boards back in. Even if the water dries up, it leaves a distinctive pattern that shows where the water came in. I also used it tucked into the headliner edges and upper cabinets to trace the windshield leak. Same leak the dealer insisted was the upper marker lights.....

Unfortunately the OP has not come back and clarified where the water is causing a concern:
-Truly IN the door, dripping like an old frige door on the ground when open? (That would be a reason to seal the window, like the OP was thinking of)
-or puddled in the frame between the door and screen? (like the door gasket was leaking)
-or leaking in the stepwell, and dripping out somewhere... (like Engineer LT's and my body sealing leaks)