I recently purchased a 2021 L and am experiencing a noticeable rattle coming from the middle row. It almost sounds like the seat isn't properly bolted in. Has anyone else experienced this? I took it to the dealership and the technician said he's heard it in 2 other Ls at his dealership. I don't know whether this is a design flaw or a defect, but would be interested to know if anyone else has experience this.