Selector Lever Check
WARNING: This page is about a different car, the 2013 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
Check for a misadjustment in the selector lever cable by matching the detents in the selector lever with those of the manual control lever in the transmission. Refer to AUTOMATIC TRANSAXLE/TRANSMISSION EXTERNAL CONTROLS for selector lever cable adjustment.