Hello dear support.
Well. .the situation is as follow
<SfToast ID="chartToast" @ref="chartToast" Width="100%" ExtendedTimeout="0" Timeout="@templateToastTimeout">
<ToastPosition X="Center" Y="Bottom"></ToastPosition>
<ToastTemplates>
<Template>
<div id="chartToastDiv" @onclick="onCloseChartClick"> </div>
<div style="width:100%; height:100%">
<SfStockChart @ref="chart" Title="" Theme="ChartTheme.Bootstrap4" EnablePeriodSelector="false" EnableSelector="true" Height="200" Width="100%" IndicatorType="@Indicators">
<StockChartCrosshairSettings Enable="true"></StockChartCrosshairSettings>
<StockChartSeriesCollection>
</StockChartSeriesCollection>
<StockChartAxes>
<StockChartAxis Name="sY" Minimum="0" ValueType="Syncfusion.Blazor.Charts.ValueType.Double"></StockChartAxis>
</StockChartAxes>
<StockChartPrimaryXAxis ValueType="Syncfusion.Blazor.Charts.ValueType.DateTime">
<StockChartAxisLabelStyle Size="8px"></StockChartAxisLabelStyle>
<StockChartAxisMajorTickLines Width="0"></StockChartAxisMajorTickLines>
</StockChartPrimaryXAxis>
<StockChartPrimaryYAxis OpposedPosition="true">
<StockChartAxisLineStyle Width="0"></StockChartAxisLineStyle>
<StockChartAxisMajorTickLines Width="0"></StockChartAxisMajorTickLines>
</StockChartPrimaryYAxis>
<StockChartChartArea>
<StockChartChartAreaBorder Width="0"></StockChartChartAreaBorder>
</StockChartChartArea>
<StockChartEvents RangeChange="onRangeChanged"></StockChartEvents>
<StockChartSeriesAnimation Enable="false" />
<StockChartCommonAnimation Enable="false" />
<StockChartIndicatorAnimation Enable="false" />
</SfStockChart>
</div>
</Template>
</ToastTemplates>
</SfToast>
and run it on mobile - let say Android.

the result will looks something like this.
In the moment you try to drag the range selector- SfToast will close.
This only happens on real device.