I am setting the status of the item to Declined as the reported behavior is due to the fact that the RowDetailsVisibilityMode is set to VisibleWhenSelected. The default behavior of RadGridView is to split the merged cell when a row with expanded row details is added. Thus, the reported issue you are is the expected one. If setting the RowDetailsVisibilityMode is removed the control will behave as expected. 

The reason for declining the item is that a possible fix for this behavior would practically interfere with the virtualization mechanism of the control. Shortly said, when the columns have their width initially set, RadGridView is aware of the column with the biggest size and performs its calculations based on it. When their size is changed on loading, the control cannot be aware of the size of a column that is not present in the viewport thus, the reported issue is observed. In order this behavior to be modified so, the engine needs to measure an element that is not yet loaded. We cannot commit ourselves to implementing this, as this would affect the virtualization of RadGridView. A possible workaround would be to avoid setting the Width of the columns initially in XAML.

The fix is available in the R1 2018 Release.

The fix is available in the R1 2018 SP2 Release.

I have a RadGridView and bind its ItemsSource and its SelectedItem to properties of the ViewModel (DataContext). I use a ViewModel for the grid items with overridden Equals and GetHashCode. When the ViewModel is created, the property bound to ItemsSource is filled and the property bound to SelectedItem is set to an item that is equal to one of the items in the collection (but not reference equal).

Problem:
When the GridView is displayed, no item is selected.

Note: I already reported this issue before: https://feedback.telerik.com/Project/143/Feedback/Details/227302-binding-itemssource-and-selecteditem-of-gridview-changes-selecteditem
but now I have managed to modify the sample project so that the problem can be reproduced. The difference to the original sample project is that Equals and GetHashCode of the Club ViewModel are overridden and the selected item is not reference equal to the item in the collection.

The issue can be solved with the help of the new added IsExpandableBinding property.

When RadGridView is bound to a ListCollectionView and the SortDescriptions are set, columns with a SortMemberPath different from the DataMemberBinding don't display the sort indicator in the column header.

In the attached example the "Status" and "ETA" columns are sorted. "Status" header does not display the indicator due to the SortMemberPath being different from the DataMemberBinding.

If you have a RadComboBox inside a ControlPanelItem, when you open the RadComboBox's dropdown and select an item, the ControlPanelItem is not closed. As a workaround, you can manually capture the mouse. Please check the attached project.

To reproduce the problem, there need to be defined a huge amount of columns(400-500). The workaround is to call the Clear method of the Columns collection of RadGridView

Available in LIB version 2018.1.205, it will be also available in the R1 2018 SP2 Release.

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.

A TargetName = "FilterIcon" should be added to the foreground setter in the trigger in the control template of the FilteringDropDown.

Available in LIB version 2018.1.122, it will be also available in the R1 2018 SP Release.

As of R1 2018 the GetCellContent method is no longer used for exporting a custom column content. Instead, the GetExportCellContent one of GridViewBoundColumnBase needs to be overriden.