dynamically generated legend doesn't show sometimes

Hello
My app is composed of tiles that shows charts created dynamically, each creats its own legendModifier like below

var legendModifier = new LegendModifier()
{
Name=”chartLegend”,
ShowLegend = true,
IsEnabled = true,
LegendPlacement = LegendPlacement.Inside,
Orientation = System.Windows.Controls.Orientation.Vertical,
Margin = new System.Windows.Thickness(3),
ShowVisibilityCheckboxes = true,
};

It shows up fine first time, if I created a second chart if I use same dataset, legend is fine in this second chart, but if I use different data in third chart, the legend won’t show up, even if I create a fourth chart chart with same data as the first chart, the legend still doesn’t show up. Attached image, thanks.