Just (hopefully) solved an annoying rattle in the hatch. 99% sure it's one of the 3rd brake light alignment bars that rubs against it's alignment hole. Went to a shop here and got some rubber grommets to prevent the contact and keep it centered. After going for a drive, the vibration was minimal, and I'm sure after I put on the trim panel, it will be muffled enough to be inaudible in the cabin.
(This doesn't appear to be a manufacturing defect, I had my hatch removed/painted for my wing install and the bars seem to have had at some point some foam or some other material that was used for this that got removed in the process.)