Last tested: Oct 26, 2018
Most likely you have chosen the Series Order option from the main EDIT > Plot menu. When using Stacked or Stacked Percentage plot (either column or bar), you have the choice to use:
Default will maintain the constant series order for each column/bar. But Descending/Ascending will order each column from low to high or vice-versa. So you could see Series A at the top of one column but at the bottom of another column.
More details on our Chart Options in our Documentation here.
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