To reproduce:
- Create a grid with ColumnGroupsViewDefinition view( Column Groups View)
- Set the AutoSizeColumnsMode to fill 
- Start the project and resize a column
- Resize a column then minimize and maximize
- The column have a different size

Workaround:
-Handle the form layout event like this:
void Form1_Layout(object sender, LayoutEventArgs e)
{
    if (this.WindowState == FormWindowState.Minimized)
    {
        this.radGridView1.GridElement.SuspendLayout();
    }
    else
    {
        this.radGridView1.GridElement.ResumeLayout(true);
    }
}