I have a 2012 Traverse that just recently developed a bad smell in the cabin. It is not from the A/C or air vents, and is most noticeable when the car sits for a while with the windows closed (not running). We had it cleaned, vacuumed, brought to the dealer...nothing can remove the smell. Nothing has spilled in the car or died in there as far as I know. Has anyone had this problem? It is a weird sour, spoiled sort of smell.