WARNING: This page is about a different car, the 2012 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Inspect the flexplate for:
any cracks.
worn ring gear teeth.
chipped or cracked ring gear teeth.
Fig 1: Inspecting Flexplate For Cracks, Worn Ring Gear Teeth And Chipped Or Cracked Ring Gear Teeth