Scrollbar scrolls unexpectedly when column width is changed. Check the following video for a reference:
http://screencast.com/t/Y6IwtREc

The content of the cell is set from .LoadContent() method and is returned from the CreateCellElement method of the column. 

One possible scenario for a fix is to change that behavior and apply directly the template as WPF DataGrid does. However, this is a huge breaking change with CreateCellElement method is widely used. The second approach is to leave the code as it is right now, return the element from method of DataTemplate and set the ContentTemplate property of the cell to that DataTemplate. This will cause the content to be loaded twice. Which will degrade the  

So, as it turns out the solution is either to introduce breaking change or degrade the performance. Both of them are against our believes and efforts to improve the controls. 

Our suggestion is to use a workaround -  setting triggers directly to the style. We do hope you understand our concerns. 

The last row is not fully visible when the gridview is scrolled to the bottom in case RowHeight is set to less than 20px. The less the row height the smaller the part of the last row which is visible. This is reproducible only in Office2013 theme. 

DataContext of rows is sometimes null when UI virtualization is enabled in the Flat group render mode.

The issue appears also without UI virtualization and in the Nested mode. It happens on ItemsSource reset of RadGridView, in case the old ItemsSource value wasn't empty. The DataContext is set to null for a brief moment before the old visuals are removed from the view, which causes issues in some scenarios related to CellTemplate

Can be observed in FirstLook demo of the RadGridView.
While resizing the demos window, radgridview's horizontal scrollbar might flicker when demos viewport size is close to the gridview size.

For the time being, an appropriate converter should be used for the bindings.

Reset by Clear, RemoveRange causes a memory leak of GridViewRow instances (or TreeListViewRow in RadTreeListView).
To work this around, you can call the Clear method of the RadGridView's Items collection and then reset the ItemsSource property.

this.radGridView.Items.Clear();
this.radGridView.ItemsSource = null;
this.radGridView.ItemsSource = newSource;
Edit: The number of instances of the GridViewRow class are relative to the number of containers which cover the visible viewport. They are kep by internal caching mechanism used for faster reuse of containers is data-reload scenarios. Containers are dettached from their previous viewmodels (DataContext).

In non virtualized scenario, the number of the live containers is the same as the number of items in the GridView's ItemsSource and when changing the source, the number remains the same as the items in the source.

We are closing this issue as we think the mentioned internal cache shouldn't be considered a memory problem but rather a powerful performance optimization internal tool for extensive data-refresh scenarios.

The RadGridView's is bound to an empty DataView and grouped by a GridViewComboBoxColumn. When adding items during runtime, setting the SelectedItem in code or selecting through the UI -> the SelectedItem remains null. 

The vertical scrollbar measure incorrectly when the control's ItemsSource is populated in its Loaded event. To reproduce this, set the ItemsSource when the control is initialized. And then populate it on Loaded. Also, to reproduce this you will need to define the columns manually.

To resolve this, populate the data on initialization of the gridview. Or delay the population to happen after the Loaded event. You can use a dispatcher for this.

The fix for this issue will be available with the next LIB (version 2018.3.1224) expected on Monday, December 24.

 Group rows which are not present in the view are not visualized when the window is maximized.

A possible solution here is to set the GroupRenderMode property to Flat.