When the ItemsSource is not set: ArgumentOutOfRangeException is thrown
When the ItemsSource is set to an empty collection: DivideByZeroException is thrown
When adding a new row and we click inside a DropDownContent of a DropDown control, the RadGridView loses focus. This way RowValidating event is called which is not expected.
In Office2016 when we increase the DPI of the Windows a left border in the header of column disappears. As a workaround you can set the Width property of all columns.
This happens only if there are many columns outside of the viewport (a scrollviewer is shown), with their TabStopMode property set to Skip.
In this case, the navigation needs some time in order to get to the next row and select the first available cell.
A possible workaround for this would be to implement a custom Keyboard Command Provider, and to replace the MoveNext command with a custom one, that moves the current cell, by setting the CurrentCellInfo property of RadGridView.