Labels (instances of the LightTextBlock control) remain on the render surface after the ItemsSource is replaced dynamically and the row or column count is changed. As a workaround, the control can be redrawn manually to clear the surface:
var temp = heatmapTest.Template;
heatmapTest.Template = null;
heatmapTest.Template = temp;
var definition = this.heatMap.Definition;this.heatMap.Definition = null;this.heatMap.Definition = definition;The labels are not positioned correctly when some of the cells are empty. Available in LIB version: 2016.1.314