Transmission Fluid Leaking problems of the 2015 Lincoln MKZ

Transmission hard shift from 1-2 and 3-4, started experiencing problem approximately 24,000 mi have taken to dealership twice(once in Feb for 4 days) and second time in Mar for 7 days), first time said it was leaking fluid and replaced "o" ring. A couple of weeks later in March returned, was getting worse, said they rebuilt the transmission. Shifts as if someone hit me in rear when increasing speed pulling away from traffic light on a city street or merging onto highway. Now makes a whining noise when accelerating from traffic light of merging, anytime shifting gears in general.