[Bug] Can't assign margin/padding to a Grid nor to a StackLayout in the form of "X X X X" or "X X".

As stated in the title I'm unable to assign a margin or a padding to a Grid or StackLayout control despite the Previewer showing it correctly and IntelliSense being ok. At compile I get an error: "Cannot convert "0 30" into Xamarin.Forms.Thickness"

Am I doing something wrong or have I encountered an error?