Some pinions have a preload with a collapsible spacer behind the drive flange. I'm not sure if the BTR axle is like this, but I would drop the rear of the propshaft, and check the tightness of the pinion nut. Don't Tarzan it. Just a gentle nip with a ring spanner so you can see if it turns. If it has loosened, a blob of loctite should hold it.
Before doing that, the Sport doesn't usually have a tool tray, and the ply cover may be glued down, but I would remove the cover, and go for a drive with the roof up, and a passenger who can lean over and do a visual on the rear end.
