Bands are drawn by creating polygons. This works best when the x coordinate increases monotonically. That is what happens in the original data case, and you get good polygons. When you reorder the x-axis values, the polygons no longer have monotonically increasing x values. So you get self-intersecting polygons.
To get non-intersecting polygons, the data set should have the x-values in the same order as the x axis values you want. Or, make the x axis linear (1-9) and use a UDF to label the values
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