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.
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.
If you have set the HorizontalContentAlignment to some other value (End, Start) and you run the application in Release mode in UWP -> the value is reset to center.