It doesn't pop off. It un-bolts. You have to bend back the corners to reach the bolts.
A few observations.
First, this thread is helpful in knowing what to do to remove the door panel:
Need Info on Roadster Door Panel Removal. The only thing I would add is to get some heavy-duty clear plastic sheeting (like a painter drop cloth or something like that) and rubber glue before launching into the project. When you go into the door, there is clear plastic sheeting glued onto the door which is difficult to get behind without damaging it.
Second, I had a horrible rattle in my RH door particularly when the window was down which I lived with for months until I took it apart to try to diagnose the issue. I should have taken photos but what I found was there is a "rail" that is connected to the tiny adjustment screw at the bottom-rear of the door that is glued at the top. Or I should say was glued. The glue fastening at the top had become detached, the rail had fallen away from the window, and was just loose inside the door (the window still worked fine and but for the rattle, I would not have know something was wrong).
To repair, I got the rail back into position holding the window, and used double sided automotive molding tape (like
https://www.autozone.com/sealants-g...n-x-5-ft-scotch-mount-molding-tape/196101_0_0) to attach the top of the rail to the insider of the door. So far, it has held. I suspect that the rail does not take kindly to the door being slammed (something that happens with the passenger side) and likely popped off because of that but who knows.
This rail might not be your issue at all. But I thought I would mention it as I could see that if the top glued-on part became un-attached how the rail could end up in the wrong position and completely bind the window in a particular position.
One other thought. While you are inside the door, it does not hurt to stick some sound-deadening material such as Dynamat (
Dynamat.com | Dynamat Xtreme and SuperLite Vibration Dampers) on the inside of the door. With the Roadster, every little bit of sound deadening helps.
