As I understand it, it was a combination of the paint formulation changes and issues with paint adhesion on aluminum surfaces.
My 2013 Grand Cherokee had an aluminum hood. Anyone who works in a body shop can rattle off the vehicles and parts of them that have paint adhesion issues on the aluminum surfaces. Dodge/Chrysler/Jeep/Ram seem to be leading that list from what he told me. Honda, Toyota, GM and finally Ford round out that list. Mostly hood surfaces, Honda also has issues with the top and trunk lids on their vehicles.
Aluminum is very difficult to coat with anything due to the fact that it corrodes very quickly. Aluminum oxide forms on the surface once you clean it off.