Ошибки отображения закруглённых кнопок

public class RoundButton : Button
    {
        GraphicsPath GetRoundPath ( RectangleF Rect, int radius )
        {
            float r2 = radius / 2f;
            GraphicsPath GraphPath = new GraphicsPath ( );
 
            GraphPath.AddArc ( Rect.X, Rect.Y, radius, radius, 180, 90 );
            GraphPath.AddLine ( Rect.X + r2, Rect.Y, Rect.Width - r2, Rect.Y );
            GraphPath.AddArc ( Rect.X + Rect.Width - radius, Rect.Y, radius, radius, 270, 90 );
            GraphPath.AddLine ( Rect.Width, Rect.Y + r2, Rect.Width, Rect.Height - r2 );
            GraphPath.AddArc ( Rect.X + Rect.Width - radius,
                                Rect.Y + Rect.Height - radius, radius, radius, 0, 90 );
            GraphPath.AddLine ( Rect.Width - r2, Rect.Height, Rect.X + r2, Rect.Height );
            GraphPath.AddArc ( Rect.X, Rect.Y + Rect.Height - radius, radius, radius, 90, 90 );
            GraphPath.AddLine ( Rect.X, Rect.Height - r2, Rect.X, Rect.Y + r2 );
 
            GraphPath.CloseFigure ( );
            return GraphPath;
        }
 
        protected override void OnPaint ( PaintEventArgs e )
        {
            base.OnPaint ( e );
            RectangleF Rect = new RectangleF ( 0, 0, this.Width, this.Height );
            GraphicsPath GraphPath = GetRoundPath ( Rect, 50 );
 
            this.Region = new Region ( GraphPath );
            using ( Pen pen = new Pen ( Color.FromArgb ( 10, 105, 122 ), 1.75f ) )
            {
                pen.Alignment = PenAlignment.Inset;
                e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
                e.Graphics.DrawPath ( pen, GraphPath );
            }
        }

button1.FlatAppearance.BorderSize = 0;
button1.FlatStyle = FlatStyle.Flat;