Either is not reproducible for me what you are telling – or I do not understand. Could you please elaborate? What do you refer to as 'the data at the top of the list'? A screenshot might help to understand.
Also please tell your Windows version? In XP I think some graphics driver setting could be involved in deciding how objects are painted by the system as well.
The issue that you have reported is reproducible in 8.71 version. This issue was introduced because of the changes made to improve vertical scrolling in GRID while displaying large number of rows. This has already been fixed internally and will be available in the next public release.