To reproduce:
- Set the AutoSizeRows and PrintGrouping properties to true.
- Add a group descriptor and then call the PrintPreview method of the grid.

Workaround:
- Use the following classes to create custom print style:
public class MyGridPrintRenderer : TableViewDefinitionPrintRenderer
{
    private RadGridView gridView;

    public MyGridPrintRenderer(RadGridView grid) : base(grid)
    {
        gridView = grid;
    }

    protected override int GetDataRowHeight(GridViewRowInfo row, TableViewRowLayoutBase rowLayout)
    {
        IVirtualizedElementProvider<GridViewRowInfo> rowElementProvider = this.gridView.TableElement.RowScroller.ElementProvider;
        GridRowElement visualRow = rowElementProvider.GetElement(row, null) as GridRowElement;
        if (visualRow is GridGroupHeaderRowElement)
        {
            return rowLayout.GetRowHeight(row);
        }
        return base.GetDataRowHeight(row, rowLayout);
    }
}

public class MyGridPrintSyle : GridPrintStyle
{
    protected override BaseGridPrintRenderer InitializePrintRenderer(RadGridView grid)
    {
        if (this.PrintRenderer != null)
        {
            this.PrintRenderer.PrintCellPaint -= renderer_PrintCellPaint;
            this.PrintRenderer.PrintCellFormatting -= renderer_PrintCellFormatting;
        }

        MyGridPrintRenderer renderer = new MyGridPrintRenderer(grid);

        renderer.PrintCellFormatting += renderer_PrintCellFormatting;
        renderer.PrintCellPaint += renderer_PrintCellPaint;

        return renderer;
    }

    private void renderer_PrintCellPaint(object sender, PrintCellPaintEventArgs e)
    {
        this.OnPrintCellPaint(sender, e);
    }

    private void renderer_PrintCellFormatting(object sender, PrintCellFormattingEventArgs e)
    {
        this.OnPrintCellFormatting(sender, e);
    }
}