When the Target version of the UWP project is Windows 1809, RadButton raises the following exception:
System.ArgumentException: Value does not fall within the expected range.
Setting the padding property does not offset the text of the button in iOS Available in the R2 2018 release.
Padding and HorizontalContentAlignment are not properly applied when Image is used.
Available in minor release 2018.3.1109. It will also be available in the R1 2019 release.