Chartjs-ChartJS multiple dataset issue. second dataset gets over 1st instead of overlaying

You should remove stacked: true from your y-axis configuration. stacked: true is for stacking each dataset on top of the previous dataset. In other words, this is for drawing each chart above the previous chart, as if the previous chart defined y = 0. That is why the height of the stacked chart becomes greater than max, although all values across all datasets are lower than max.