Last tested: Jul 10, 2019
If you see the above error on a boxplot visualization, change the chart type to line and go to Edit Visualization -> Y. We shouldn't have extra Y-axis in the line visualization configuration. Boxplots can only have a single Y-axis value. The boxplot inherits the config we had on the line visualization.
Also, check if the Y-axis is showing the 5 measures or "stacked" - it needs to be the 5 measures you want to check.