Hi Steven ,
We have implemented a new feature "UseNativeFloatWindow" in DockingManager for Floating windows.By setting UseNativeFloatWindow as True ,the NativeFloatWindow which is inherited from window is created for FloatState. We recommend you to use the UseNativeFloatWindow property to resolve the issue that you have faced by using normal FloatWinodw inherited from Pop up.
For more information about NativeFloatWindow, please refer the below link
[User Guide]
http://help.syncfusion.com/ug/wpf/tools/default.htm#!documents/nativefloatwindow.htm
Please let us know if you have any concerns.
Regards,
Yasvanth