Something similar happened to me, took it back to the dealership, did some "upgrades" couple minutes later I got my Mustang back good as new. They didn't charge me anything, could have also been that I just recently bought it, and I'm still under full warranty. Hope this helps and offers any insight to solving the issue.
2012 Ford Mustang Black GT Custom Convertible
Mustang Club of America | Mustang Owners of Southeast Michigan