Full error message: No generic method 'Sum' on type 'System.Linq.Enumerable' is compatible with the supplied type arguments and arguments. No type arguments should be provided if the method is non-generic."

Showing in design time, working at run time. 

WPF Controls Samples -> GridView with Data Virtualization -> Edit UnitPrice and press Enter -> press ESC -> press Control+End.

Workaround: press ESC one more time or commit the edit before pressing  Control+End.
* works fine with QueryableCollectionView.

The problem can be reproduced only when the previously focused element is in ToolBar or RadToolBar. It is not reproducible in the default scenario. 

Should be resolved with lib version 2015.2.713.

GridViewColumnGroup.HeaderTemplate is not respected in Windows8, Windows8Touch and ExpressionDark themes. Instead, the name of the column group is its content.

This is reproducible with both StyleManager and Implicit Styles.

Should be resolved with lib version 2015.2.720.

Will be available with LIB version 2015.3.1026.

As a workaround, one can look this up by accessing the Object/DbContext directly.

Workaround is to specify that the format string should contain only the required member path:

<telerik:GridViewDynamicHyperlinkColumn Header="ID" DataMemberBinding="{Binding ID}" NavigateUrlMemberPaths="WebUrl" NavigateUrlFormatString="{} {0}"  TargetName="_blank"/>

A kind of a workaround for the user: resize any column/the entire window or collapse the row details.

The designer crashes with this exception:
InvalidOperationException: 'GridViewColumnGroupRow' TargetType does not match type of element 'GridViewColumnGroupRow'.

See the attached screenshot. It's from a new project, after clean and rebuild.

Visual studio: 2015
Telerik UI for wpf: 2015.2
Implicit styles, Windows8 theme.

* The problem is not theme specific. As a workaround, use no xaml binaries instead of xaml files.