The behavior you have encountered is expected. The way to prevent this is to handle the PreviewKeyDown event of the RadGridView and implement logic that checks these two conditions:
1) If the current cell is the rightmost one and the e.Key==Key.Right
2)If the current cell is the leftmost one and the e.key==Key.Left
The set : e.handled = true;
Please let us know if this fits in your scenario.
All the best,
the Telerik team
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