Hood is aluminum and very sensitive to prep so any contamination can cause the paint to lift. There was even a TSB about it for the S197 cars:
http://www.ppg.com/coatings/refinis...info_aluminumPanelsCorrosionTip_tsb062515.pdf
http://www.ppg.com/coatings/refinis...info_aluminumPanelsCorrosionTip_tsb062515.pdf