New data that is displayed is aligned with the first column on the left of the chart (data grid), but the column headers remain aligned where they were previously (i.e. scrolled right). Thus the column headers and data rows are out of alignment.
You need to enable the Lock Column. When you click on the dimension field you will get this option. Setting Lock Column to true for a dimension or series column will make the column - and all columns to the left of it - retain position when horizontally scrolling the grid. Using Lock Column can be useful with grids that have many columns that need to be scrolled through but also have a few key fields that always need to be seen in order to identify records.