Applying ChartTrackBallBehavior to a CartesianChart with ScatterLine/ScatterPoint series does not take any effect.

On the Chart control, the labels of the Legend are in a different font than everywhere else on iOS.

As of the latest release (10/04/2019) RadPieChart with a PieSeries having LabelBinding set to a property name, and ShowLabels set to True, with the list of data bound to ItemsSource containing one or more empty pie slices (a null in the list), causes a System.Reflection.TargetException to be thrown on load of the page containing the chart in iOS (this scenario works fine in UWP).

I am using the latest available Visual Studio 2019 (16.3.5) and the latest available Xamarin.Forms package (4.2.0.848062) and testing on an iPad with iOS 13.1.  The reason I need to have a null value in the list is so that the custom color palette I'm applying will always apply the same colors to the same data points (pie slices), even though in some cases, zero or one or two of the three pie slices will have no data value (and so should not appear in the chart, but still "use up" the corresponding color in the 3 colors of the palette).

In the 08/02/2019 release, this scenario worked fine in iOS (the 09/13/2019 release had the https://feedback.telerik.com/xamarin/1431067-chart-ios-invalidcastexception-is-thrown-when-the-chart-is-loaded issue, which is now resolved in the 10/04/2019 release, but which prevented my testing in iOS since in my app I had RadCartesianCharts on the same pages as the RadPieCharts).

The newly broken functionality in iOS could possibly be related to two other items that are marked completed:
https://feedback.telerik.com/xamarin/1366403-piechart-tooltip-behavior-is-not-working-properly (in 10/04/2019 release)
https://feedback.telerik.com/xamarin/1365842-chart-null-value-support (in R3 2018 SP release)

If you clear the collection bound to the series ItemsSource and add new items to it, the changes are not reflected on the Chart

When the Chart is zoomed, new labels are not rendered on iOS.

When the series data is updated and axis labels are redrawn, occasionally the default DateTime format is shown in DateTimeContinuousAxis.

Loading Chart on iOS raises an exception of type InvalidCastException.

When you update the data in the chart so that the vertical axis values are changed - the annotation does not properly update and stays at the same location.

After setting the MajorLinesVisibility property to GridLineVisibility.Xy only the Y lines are showing up.

If customers set bindings to these properties and try to set range from negative to positive values (e.g. from -0.5 to 0.5) the bindings are not applied as expected.

If you have a Chart with BarSeries and TooltipBehavior defined, the tooltip of each bar is shown only when the user taps in the area around the tip of the bar.

The expected behavior is the tooltip to be displayed when clicking anywhere on the bar.

When you set custom stroke to ScatterLineSeries, the colors in the RadLegend are not updated.

When you have some Series defined and dynamically clear and add new Series, those are not displayed correctly on iOS - it seems the vertical axis is not extended, and all the data points are visualized on the horizontal axis.

Setting SelectedPointOffset and RadiusFactor in DonutSeries or PieSeries causes unexpected behavior when selecting a pie piece in the chart.

Once the data of the bar chart is changed, the selection behavior does not fire. The issue is reproducible when the chart is placed inside AnimationPanel,

The issue seems to be down to the width - either calculated or set. Some widths seem to cause the lines to appear - refer to the attached chart_grey_lines.png file.

Workaround: manually calculate the screen width upon load and to set the width to a corresponding lookup value

SelectionChanged event of the Chart SelectionBehavior is not raised for LineSeries when DataPointSelectionMode is "Single" and  SeriesSelectionMode is "None".  

If we have a Chart with combined barseries and lineseries, and the lineseries is added first, the bars are misaligned - they are not placed in the center of the axis label on Android.

As a workaround, make sure to add first the barseries, then the lineseries.

When Custom Palette is used and FillColor is set, the color is not applied to the line series.

As a workaround set the both properties of the PaletteEntry: FillColor and SrtokeColor: 

<telerikChart:PaletteEntry  FillColor="Red" StrokeColor="Red" />