now i'm using xamarin.forms
especially i use Application.Current.Properties aka mobile dictionary for saving some data.
in my case i store some token and url.
then recently i add BackGroundColor for providing theme.
BackGroundColor type was Color (Xamarin.Forms.Color) then after saving Color,
next start all of data(some token, url..) was deleted.
when i changed BackGroundColor type to string(Color hex) then it works