Mine recently started rattling around. Thought it was my dashcam but it's still snug. While checking it I noticed the mirror was loose when I bumped it.
By loose I mean it doesn't appear to be the bracket connecting the mirror to the windshield, but loose on what I assume is a ball and socket type connector. I wonder if there's a way to tighten it. Snapped a photo of the back of the back of the mirror and looks like there's a small screw hole or something, but haven't investigated further yet:
