* Workaround: commit the edit before removing the item
* Works fine with the old Nested mode

The issue is reproducible with Q1 2015 SP1 version. With Q1 2015 it is not.
In order to reproduce it, add at least one empty cell. When you try opening the excel file you get the an error that Excel will try to recover the file.

Should be resolved with LIB version 2015.1.413.

Workaround:

Define an implicit Style targeting GridViewRow UI element under Window.Resources or RadGridView.Resources section.

The problem should be resolved with lib version 2016.1.125.

StackOverFlowException when the GroupMemberPath is set to a different path to the data member and the column is grouped, and filtered.

As an example I add a column to the grid:
columns.Add(new GridViewDataColumn() { DataMemberBinding = new Binding("CustomerId"), GroupMemberPath = "CustomerName", SortMemberPath="CustomerName", Width = 300 });

When the grid appears, drag the CustomerId column to the grouping area
Click the filter icon on the CustomerId column
Click a checkbox in the filtering control to select an item
Exception occurs

It should be resolved with lib version 2015.1.504.

There is a mistake in the text shown in the GroupPanel of RadGridview in french.
it should be something like "Glissez un en-tête de colonne et déposez-le ici.."

Update: Before our change the GridViewGroupFooterCell content was right aligned and the GridViewFooterCell content was left aligned. We decided to unify them by setting default left alignment to both. This can be easily modified by changing the Column FooterTextAlignment property to Right or by using the following implicit styles: 

<Style TargetType="telerik:GridViewGroupFooterCell" BasedOn="{StaticResource GridViewGroupFooterCellStyle}">
    <Setter Property="HorizontalContentAlignment" Value="Right"/>
</Style>
<Style TargetType="telerik:GridViewFooterCell" BasedOn="{StaticResource GridViewFooterCellStyle}">
    <Setter Property="TextAlignment" Value="Right"/>
</Style>

The fix is available in R3 2017 of UI for WPF.

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.