In Datagrid [or] GridView Paging when last page contains less number of records than the page size, the pager will move upward.
Datagrid PageSize = 15 and 75 records are returned from DB, then pager will show 5 pages. If 70 records are returned, pager will show 5 pages and if the4th ( last page) page is clicked pager will move upwards, i.e pager will take the position just after the 10th record and not at the end of the datagrid as in other pages.
If you want to fix that pager, add a css to pagerstyle.
<PagerStyle CssClass=”pager” Wrap=”True” Mode=”NumericPages” Position=”Bottom”></PagerStyle>