A text offset of 2 pixel - scaled to screen resolution - is hardcoded for textboxscrollup controls, which is what causes the text to end up scrolling higher than the original position.

Adding a <scrollYOffset> property to textboxscrollup (default set to 2 for backwards compatibility) allows skins to adjust the offset and prevent text scrolling higher than the original position.

A test version was posted in Team forum: http://forum.team-mediaportal.com/threads/text-in-scrollbox-scrolls-higher-than-original-position.115663/#post-957737

h4. Steps to Reproduce
Go to any window that uses textboxscrollup, e.g. Videos Plot/Description
Observe the text as it starts to scroll, scrolls higher than the original position.
The issue is more obvious on skins that use larger fonts.