Hi,
please try to recreate this bug.
Latest version of syncfusion 14.1.0.46
Visual Studio 2015
Windows Forms project
Add navigationdrawer control
Add DrawerHeader and change the default BackColor to any other color.
Button for toggling the drawer and start
When the drawer is toggled one new DrawerHeader is creating from nowhere
It is not visible in item collection of the navigationdrawer until you restart the project.