I'm using Addictive keys softsynth. I play back the piano part and when I stop playback the piano sustains as if the sustain peddal is pressed. Any ideas why this would happen?

Did you record sustain pedal events? 

If so, this totally happens to me  if I pause in the middle of the phrase, before an up pedal event has happened, the note sustains. Just like a real piano.

I don't have a problem with this behavior, although I suppose an argument could be made that sustain pedal events should be treated like "zero controllers on stop" or whatever that preference setting is.

On the other hand, if it is sustaining because somewhere a MIDI note-off has been ignored... that's a different issue.

Yeah, it seems to do it before an up pedal event. i don't remember this ever happening in 8.53 or X1 but it is what it is I guess.