Well I've done all sorts of tests drive, memory, etc and everything says it's fine.
My final observation is that if I have the zoom level way down it scrolls fine. If zoom in to about 6 seconds showing on the screen it scrolls perfectly. It's just some of the intermediate settings. If anyone has time try setting up 12 RT at 120 BPM and play with the zoom level and see if you get stuttering. BTW I have the audio buffers at 500 and never misses a beat.