If the size of the text and icons on the screen is set to larger and the font of the text is set to 12 pixels. Letters that have tails below (such as: g, j, y) are not shown properly inside the text box. 

Workaround:

As a workaround one can set the minimum height of the text box to be as the height of the text and allow multi lines.

int textHeight = TextRenderer.MeasureText(this.radTextBox1.Text, this.radTextBox1.Font).Height;this.radTextBox1.TextBoxElement.TextBoxItem.MinSize = new Size(0, textHeight);this.radTextBox1.TextBoxElement.TextBoxItem.InvalidateMeasure();this.radTextBox1.TextBoxElement.TextBoxItem.UpdateLayout();this.radTextBox1.Multiline = true;