To reproduce: 

1. Add a RadGridView, set ShowRowHeaderColumn to false, AutoSizeColumnsMode to Fill and Dock to Fill. 

2. Add 3 columns and 1 row. 

3. Start the application and click the leftmost cell, you will notice that the header will move with one pixel to the right. 

4. Click the rightmost cell and you will notice the header moving one pixel to the left