Hi
Scrolling time can effect how smooth it looks.
If, for example you are scrolling text from top to bottom of the screen the smoothness will depend on the duration of the text clip. If this is rather short, say only a few seconds then the text has to move more pixels between each frame and this can produce a slightly jerky movement. Give more time for the text to scroll and it should appear smoother. Exporting with a constant frame rate may also smooth the result. If it seems uneven and not just "jumpy" it may be linked frame rate try making input and output frame rates the same. Worth trying
Nat