I test drove an srt yesterday. I pulled off the lot and accelerated to about 40mph then braked for the light and the car would downshift real hard from 2nd into neutral while the car was still in drive. I had to put it into neutral or park then back to drive for it to go. I thought that was strange but it happened almost everytime I slowed down. The only way it stopped was I finally used the shifter to manually change gears and take it back. Does this sound like a transmission problem or was I doing something wrong?

It's been awhile since I had an automatic but last time I checked D was for drive.