Actually, I was thinking of the power awning which has a leg that rests on the sidewall. Wasn't thinking about this being a manual awning...which only mounts on the bottom and the top. So, it could be the door or the front edge of the metal wrapped awning.
Maybe try some plastic wrap to cover the front edge of the awning just for process of elimination. If there is still a whistle...move to the door.
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